Disable rubocop Style/RegexpLiteral

[beauraF]

We noticed a formatting difference for regex between rubocop and syntax_tree, which causes back-and-forth changes between the two tools.

For example, this is what the code looks like when formatted by rubocop:

let(:gotcha_with_check_deleted_lines) do
  {
    text: 'Couchbase model gotcha',
    file_regexp: %r{^app/models/.*\.rb},
    keywords: [/ attribute :/],
    check_deleted_lines: true,
  }

And this is what it looks like when formatted by syntax_tree:

let(:gotcha_with_check_deleted_lines) do
 {
   text: 'Couchbase model gotcha',
   file_regexp: %r{^app/models/.*\.rb},
   keywords: [%r{ attribute :}],
   check_deleted_lines: true,
 }

Therefore, I propose disabling Style/RegexpLiteral in config/rubocop.yml and letting syntax_tree handle regex formatting.