Bump rspec and friends to 3.11 in omnibus

What does this MR do?

This enables us to take advantage of new counter methods in
rspec-expectations that allows for checking for duplicates and/or
an expected number of items (e.g. include(‘some string’).twice

Latest version is 3.12 - but inspec-core has a <= constraint for 3.11

Changelog: changed
Signed-off-by: Jason Young <jyoung@gitlab.com>

Related issues

Upgrade Rspec in Omnibus to >= 3.10.0 (#7294 - closed)

See also Apply proxy_custom_buffer_size option to API lo... (!6481 - merged)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened

Closes #7294 (closed)