Handle Ruby 3.1 Style/HashSyntax Rubocop failures

https://gitlab.com/gitlab-org/gitlab/-/jobs/3918495099 has such failures as:

ee/spec/requests/api/resource_weight_events_spec.rb:8:47: C: [Correctable] Style/HashSyntax: Omit the hash value.
  let_it_be(:issue) { create(:issue, project: project, author: user) }
                                              ^^^^^^^
ee/spec/requests/api/resource_weight_events_spec.rb:83:43: C: [Correctable] Style/HashSyntax: Omit the hash value.
    create(:resource_weight_event, issue: issue, weight: 2)
                                          ^^^^^
ee/spec/requests/api/rubygem_packages_spec.rb:10:76: C: [Correctable] Style/HashSyntax: Omit the hash value.
  let_it_be(:personal_access_token) { create(:personal_access_token, user: user) }

As @mkaeppler mentioned in &9684 (comment 1270023917):

Ruby 3.1 introduced a new short-hand syntax for passing keyword arguments:

val = 42
m(val: val)

can now be:

val = 42
m(val:) # passes `val`

https://rubyreferences.github.io/rubychanges/3.1.html#values-in-hash-literals-and-keyword-arguments-can-be-omitted

This is flagged by a Cop when targeting Ruby 3.1 or above: https://gitlab.com/gitlab-org/ruby/gems/gitlab-dangerfiles/-/jobs/3733585196

We may want to add TODOs for these since we cannot fix this until we are actually on 3.1+.