build(deps): update csv-string requirement from 3.1.3 to 3.1.5

Updates the requirements on [csv-string](https://github.com/touv/node-csv-string) to permit the latest version.
- [Release notes](https://github.com/touv/node-csv-string/releases)
- [Commits](https://github.com/touv/node-csv-string/commits/v3.1.5)

Signed-off-by: dependabot[bot] <support@dependabot.com>

package.json

@@ -23,7 +23,7 @@
     "async": "2.6.1",
     "boom": "7.2.0",
     "csv-streamify": "4.0.0",
-    "csv-string": "3.1.3",
+    "csv-string": "3.1.5",
     "debug": "3.1.0",
     "dottie": "2.0.0",
     "glob": "7.1.3",