[Identity] Moving @types/stoppable to the devDependencies (Azure#20070)

`@types/stoppable` was added by mistake to the `dependencies` of the `package.json` of `@azure/identity`. This package is only used to build the TypeScript code, and not used on runtime, so it should have been placed on the `devDependencies` from the beginning. This package has no effect during runtime.

Fixes Azure#20024

Author: sadasant

sdk/identity/identity/CHANGELOG.md

@@ -15,6 +15,8 @@
 
 ### Other Changes
 
+- Moved the `@types/stoppable` dependency to the `devDependencies`.
+
 ## 2.0.1 (2021-10-28)
 
 ### Features Added

sdk/identity/identity/package.json

@@ -112,7 +112,6 @@
     "@azure/msal-common": "^4.5.1",
     "@azure/msal-node": "^1.3.0",
     "@azure/msal-browser": "^2.16.0",
-    "@types/stoppable": "^1.1.0",
     "events": "^3.0.0",
     "jws": "^4.0.0",
     "open": "^8.0.0",
@@ -132,6 +131,7 @@
     "@types/node": "^12.0.0",
     "@types/uuid": "^8.0.0",
     "@types/chai": "^4.1.6",
+    "@types/stoppable": "^1.1.0",
     "chai": "^4.2.0",
     "cross-env": "^7.0.2",
     "dotenv": "^8.2.0",