package.json,package-lock.json: remove @actions/github dependency

Remove @actions/github since we don't actually seem to use this
dependency in the action. We can add this back in if / when we do need
it, otherwise it is just causing noise with dependabot updates for no
reason.

Updates #cleanup

Signed-off-by: Mario Minardi <mario@tailscale.com>

Author: mpminardi

package-lock.json

@@ -19,7 +19,6 @@
     "@actions/cache": "^5.0.2",
     "@actions/core": "^2.0.2",
     "@actions/exec": "^2.0.0",
-    "@actions/github": "^7.0.0",
     "@actions/tool-cache": "^3.0.0",
     "semver": "^7.7.3"
   },