Bump crazy-max/ghaction-import-gpg from 5 to 6

Bumps [crazy-max/ghaction-import-gpg](https://github.com/crazy-max/ghaction-import-gpg) from 5 to 6.
- [Release notes](https://github.com/crazy-max/ghaction-import-gpg/releases)
- [Commits](crazy-max/ghaction-import-gpg@v5...v6)

---
updated-dependencies:
- dependency-name: crazy-max/ghaction-import-gpg
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/proto-registry.yml

@@ -38,7 +38,7 @@ jobs:
           buf_token: ${{ secrets.BUF_TOKEN }}
       - name: Import GPG key
         id: import_gpg
-        uses: crazy-max/ghaction-import-gpg@v5
+        uses: crazy-max/ghaction-import-gpg@v6
         with:
           # Use a key associated with the provenanceio-bot github account.
           gpg_private_key: ${{ secrets.BOT_GPG_PRIVATE_KEY }}