Exclude trailing spaces from commit search queries

What does this MR do and why?

• Contributes to #386479 (closed)
• Feature flag: #386825 (closed)

Problem

Trailing spaces in the search query prevent users from finding commits.

Solution

Remove trailing spaces from the search query.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable feature flag Feature.enable(:commit_search_trailing_spaces)
2. Visit commits page and search by commit message that has trailing spaces
3. You should see the result for a query without trailing spaces

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.