build(deps): bump @actions/core in /.github/actions/send-email

Bumps [@actions/core](https://github.com/actions/toolkit/tree/HEAD/packages/core) from 1.2.6 to 1.9.1.
- [Release notes](https://github.com/actions/toolkit/releases)
- [Changelog](https://github.com/actions/toolkit/blob/main/packages/core/RELEASES.md)
- [Commits](https://github.com/actions/toolkit/commits/HEAD/packages/core)

---
updated-dependencies:
- dependency-name: "@actions/core"
  dependency-type: direct:production
...

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

Author: dependabot[bot]

.github/actions/send-email/package-lock.json

@@ -14,7 +14,7 @@
   "author": "Firebase <[email protected]> (https://firebase.google.com/)",
   "license": "Apache-2.0",
   "dependencies": {
-    "@actions/core": "^1.2.6",
+    "@actions/core": "^1.9.1",
     "mailgun.js": "^3.3.0"
   },
   "devDependencies": {