Bump underscore from 1.8.3 to 1.12.1 (#15354)

Bumps [underscore](https://github.com/jashkenas/underscore) from 1.8.3 to 1.12.1.
- [Release notes](https://github.com/jashkenas/underscore/releases)
- [Commits](https://github.com/jashkenas/underscore/compare/1.8.3...1.12.1)

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

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

package.json

@@ -225,7 +225,7 @@
     "typemoq": "^0.3.2",
     "typescript": "4.2.0-dev.20201207",
     "typescript-formatter": "7.1.0",
-    "underscore": "^1.8.2",
+    "underscore": "^1.12.1",
     "vinyl": "^2.0.0",
     "vinyl-fs": "^3.0.0",
     "vscode-debugprotocol": "1.44.0",