fix: correct package naming in "browser" fields (#625)

Webpack 5 makes browser polyfills explicit. Webpack detects `@aws-sdk/hash-node` as something that includes node features to potentially pollfill while using `@aws-crypto/sha256-universal`. This can be resolved via a webpack config, but better to handle it here.

packages/sha256-universal/package.json

@@ -26,7 +26,7 @@
   "main": "./build/index.js",
   "types": "./build/index.d.ts",
   "browser": {
-    "@aws/hash-node": false,
+    "@aws-sdk/hash-node": false,
     "crypto": false
   }
 }