fix rubocop fernignore (#165)

Co-authored-by: jsklan <[email protected]>

Author: fern-support

.fernignore

@@ -2,7 +2,7 @@ lib/square_legacy/
 lib/square_legacy.rb
 Gemfile
 Rakefile
-.rubocop
+.rubocop.yml
 square.gemspec
 .gitignore
 test/