Updating select helper doc [ci skip]
Fix misspelling in references docs
Update documentation on group method to indicate it takes an array

The group method also takes an array, however this isn't immediately
clear by reading the source since it delegates this method. If you
trace it back to the AREL building you can see that it does support
an array.

Shoutout to @betovelandia for pointing this out.
Mention required glob param name in match docs for mapper

THe match documentation doesn't mention any requirement of the
parameter name requirement for matches. However, including a
bare glob character without a variable assignment causes a
parse error.
Append link to bad code to backtrace when exception is SyntaxError
Clarify environment_name for logs

[ci skip]
Replace trivial regexp with string or index, twice as fast
Merge pull request #14521 from kreynolds/replace-regexp-with-include-or-string

Replace trivial regexp with string or include, twice as fast
Fix tests not unsubscribing from Notifications.

See https://github.com/rails/rails/blob/master/activesupport/lib/active_support/notifications.rb#L131
Ensure we are returning either `true` or `false` for `#==`

460eb83d cused `ActiveRecord::Base#==` to sometimes return `nil` in some cases,
this ensures we always return a boolean value. Also fixed a similar problem in
AR reflections.
copy edit [ci skip]
Merge branch 'master' of github.com:rails/docrails
Merge pull request #14526 from chancancode/fix_ar_equality

Ensure we are returning either `true` or `false` for `#==`
Merge pull request #14524 from tgxworld/fix_unsubscribe_from_notifications

Fix tests not unsubscribing from Notifications.
Merge pull request #13890 from achempion/syntax-error-backtrace

append link to bad code when error type is SyntaxError
Refactor test to use DdlHelper.

Follow-Up to https://github.com/rails/rails/pull/14400

This ensures that all tables are removed after each test and thereby
allowing us to run the tests in a random order.