Bump rubocop-ast from 0.7.0 to 0.7.1 (#14899)

Bumps [rubocop-ast](https://github.com/rubocop-hq/rubocop-ast) from 0.7.0 to 0.7.1.
- [Release notes](https://github.com/rubocop-hq/rubocop-ast/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop-ast/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop-ast/compare/v0.7.0...v0.7.1)

Signed-off-by: dependabot[bot] <support@github.com>

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

Gemfile.lock

@@ -543,9 +543,8 @@ GEM
       rubocop-ast (>= 0.5.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 1.4.0, < 2.0)
-    rubocop-ast (0.7.0)
+    rubocop-ast (0.7.1)
       parser (>= 2.7.1.5)
-      strscan (>= 1.0.0)
     rubocop-rails (2.8.1)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
@@ -606,7 +605,6 @@ GEM
       multi_json (~> 1.8)
     strong_migrations (0.7.1)
       activerecord (>= 5)
-    strscan (1.0.3)
     temple (0.8.2)
     terminal-table (1.8.0)
       unicode-display_width (~> 1.1, >= 1.1.1)