Bump rake_gpg from 0.18.0 to 0.20.0

Bumps [rake_gpg](https://github.com/infrablocks/rake_gpg) from 0.18.0 to 0.20.0.
- [Commits](infrablocks/rake_gpg@v0.18.0...v0.20.0)

---
updated-dependencies:
- dependency-name: rake_gpg
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -103,9 +103,9 @@ GEM
       octokit (>= 4.16, < 9.0)
       rake_factory (~> 0.23)
       sshkey (~> 2.0)
-    rake_gpg (0.18.0)
-      rake_factory (~> 0.23)
-      ruby_gpg2 (~> 0.6)
+    rake_gpg (0.20.0)
+      rake_factory (~> 0.33)
+      ruby_gpg2 (~> 0.12)
     rake_leiningen (0.38.0)
       rake_dependencies (~> 3.7)
       rake_factory (~> 0.33)