Merge branch 'futher_diff_preview_default_value_changes' into 'master'

Change final default value of show_diff_preview_message

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/149716



Merged-by: Miguel Rincon <mrincon@gitlab.com>
Approved-by: Miguel Rincon <mrincon@gitlab.com>
Co-authored-by: Joseph Snyder <joe.snyder@kitware.com>