Enable FF ci_fix_rules_if_comparison_with_regexp_variable by default

What does this MR do and why?

This MR enables the feature flag ci_fix_rules_if_comparison_with_regexp_variable by default.

It's been enabled in GitLab.com since May 31st.

• Rollout issue: #359740 (closed)
• Bug issue: #35438 (closed)
• Introduced in: !85310 (merged)

MR acceptance checklist

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