Bump up babel-cli version to fix security alert

[ackintosh]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\. If contributing template-only or documentation-only changes which will change sample output, be sure to build the project first.
• Filed the PR against the correct branch: master, 4.1.x, 5.0.x. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

Updated the babel-cli version to fix the alert below.

Regular Expression Denial of Service
https://www.npmjs.com/advisories/786

$ cd samples/client/petstore/javascript-flowtyped
$ npm audit

                       === npm audit security report ===

┌──────────────────────────────────────────────────────────────────────────────┐
│                                Manual Review                                 │
│            Some vulnerabilities require your attention to resolve            │
│                                                                              │
│         Visit https://go.npm.me/audit-guide for additional guidance          │
└──────────────────────────────────────────────────────────────────────────────┘
┌───────────────┬──────────────────────────────────────────────────────────────┐
│ Low           │ Regular Expression Denial of Service                         │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Package       │ braces                                                       │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Patched in    │ >=2.3.1                                                      │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Dependency of │ babel-cli [dev]                                              │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Path          │ babel-cli > chokidar > anymatch > micromatch > braces        │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ More info     │ https://npmjs.com/advisories/786                             │
└───────────────┴──────────────────────────────────────────────────────────────┘
found 1 low severity vulnerability in 6034 scanned packages
  1 vulnerability requires manual review. See the full report for details.

Used npx cli tool to know how we should update the package.json and .babelrc.

$ cd samples/client/petstore/javascript-flowtyped
$ npx babel-upgrade --write


🙌  Thanks for trying out https://github.com/babel/babel-upgrade !

Updating closest package.json dependencies
Index: /Users/akihito1/src/github.com/ackintosh/openapi-generator-1/samples/client/petstore/javascript-flowtyped/package.json
===================================================================
--- /Users/akihito1/src/github.com/ackintosh/openapi-generator-1/samples/client/petstore/javascript-flowtyped/package.json      Before Upgrade
+++ /Users/akihito1/src/github.com/ackintosh/openapi-generator-1/samples/client/petstore/javascript-flowtyped/package.json      After Upgrade
@@ -21,12 +21,13 @@
   "dependencies": {
     "portable-fetch": "^3.0.0"
   },
   "devDependencies": {
-    "babel-cli": "^6.26.0",
-    "babel-core": "^6.26.3",
-    "babel-plugin-transform-flow-strip-types": "^6.22.0",
+    "@babel/cli": "^7.0.0",
+    "@babel/core": "^7.0.0",
+    "@babel/plugin-transform-flow-strip-types": "^7.0.0",
     "babel-preset-react-app": "^3.1.1",
     "flow-copy-source": "^1.3.0",
-    "rimraf": "^2.6.2"
+    "rimraf": "^2.6.2",
+    "@babel/preset-flow": "^7.0.0"
   }
 }
\ No newline at end of file


Updating .babelrc config at .babelrc
Index: .babelrc
===================================================================
--- .babelrc    Before Upgrade
+++ .babelrc    After Upgrade
@@ -1,8 +1,9 @@
 {
   "presets": [
-    "react-app"
+    "react-app",
+    "@babel/preset-flow"
   ],
   "plugins": [
-    "transform-flow-strip-types"
+    "@babel/plugin-transform-flow-strip-types"
   ]
 }
\ No newline at end of file

[ackintosh]

cc: @jaypea @CodeNinjai @frol @cliffano

[wing328]

LGTM