Bump @types/node from 15.9.0 to 15.12.0 in /src/vscode-bicep (#3026)

Bumps [@types/node](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/node) from 15.9.0 to 15.12.0.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/node)

---
updated-dependencies:
- dependency-name: "@types/node"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/vscode-bicep/package-lock.json

@@ -199,7 +199,7 @@
     "@types/cytoscape": "^3.14.15",
     "@types/jest": "^26.0.23",
     "@types/mocha": "^8.2.2",
-    "@types/node": "^15.9.0",
+    "@types/node": "^15.12.0",
     "@types/react": "^17.0.9",
     "@types/react-dom": "^17.0.6",
     "@types/react-test-renderer": "^17.0.1",