Bump rubocop-performance from 1.20.2 to 1.21.0 (#394)

Bumps [rubocop-performance](https://github.com/rubocop/rubocop-performance) from 1.20.2 to 1.21.0.
- [Release notes](https://github.com/rubocop/rubocop-performance/releases)
- [Changelog](https://github.com/rubocop/rubocop-performance/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-performance@v1.20.2...v1.21.0)

---
updated-dependencies:
- dependency-name: rubocop-performance
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -61,9 +61,9 @@ GEM
       rubocop (~> 1.41)
     rubocop-factory_bot (2.25.1)
       rubocop (~> 1.41)
-    rubocop-performance (1.20.2)
+    rubocop-performance (1.21.0)
       rubocop (>= 1.48.1, < 2.0)
-      rubocop-ast (>= 1.30.0, < 2.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
     rubocop-rake (0.6.0)
       rubocop (~> 1.0)
     rubocop-rspec (2.27.1)