chore(deps): bump simple-git from 2.19.0 to 2.21.0 (actions#80)

Bumps [simple-git](https://github.com/steveukx/git-js) from 2.19.0 to 2.21.0.
- [Release notes](https://github.com/steveukx/git-js/releases)
- [Changelog](https://github.com/steveukx/git-js/blob/master/CHANGELOG.md)
- [Commits](steveukx/git-js@v2.19.0...v2.21.0)

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

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

package.json

@@ -36,7 +36,7 @@
   "dependencies": {
     "@actions/core": "^1.2.6",
     "axios": "^0.21.0",
-    "simple-git": "^2.19.0"
+    "simple-git": "^2.21.0"
   },
   "devDependencies": {
     "@types/node": "^12.12.54",