vim-patch:9.1.1906: filetype: not all Ruby files are recognized (#36526)

Problem:  filetype: not all Ruby files are recognized
Solution: Detect *.rbi and Brewfile as ruby filetype
          (botantony).

- `rbi` is a file extension used by Sorbet, typechecker for Ruby:
   https://sorbet.org/docs/rbi

- `Brewfile` is a bundler file for Homebrew package manager:
   https://docs.brew.sh/Brew-Bundle-and-Brewfile

closes: vim/vim#18697

efc3be77bb

Co-authored-by: botantony <antonsm21@gmail.com>

test/old/testdir/test_filetype.vim

@@ -692,7 +692,9 @@ func s:GetFilenameChecks() abort
     \ 'rrst': ['file.rrst', 'file.srst'],
     \ 'rst': ['file.rst'],
     \ 'rtf': ['file.rtf'],
-    \ 'ruby': ['.irbrc', 'irbrc', '.irb_history', 'irb_history', 'file.rb', 'file.rbw', 'file.gemspec', 'file.ru', 'Gemfile', 'file.builder', 'file.rxml', 'file.rjs', 'file.rant', 'file.rake', 'rakefile', 'Rakefile', 'rantfile', 'Rantfile', 'rakefile-file', 'Rakefile-file', 'Puppetfile', 'Vagrantfile'],
+    \ 'ruby': ['.irbrc', 'irbrc', '.irb_history', 'irb_history', 'file.rb', 'file.rbi', 'file.rbw', 'file.gemspec', 'file.ru', 'Gemfile', 'file.builder',
+    \         'file.rxml', 'file.rjs', 'file.rant', 'file.rake', 'rakefile', 'Rakefile', 'rantfile', 'Rantfile', 'rakefile-file', 'Rakefile-file',
+    \         'Puppetfile', 'Vagrantfile', 'Brewfile'],
     \ 'rust': ['file.rs'],
     \ 'sage': ['file.sage'],
     \ 'salt': ['file.sls'],