Use case-insensitive comparison for commit SHAs

What does this MR do and why?

Contributes to #453996 (closed)

Problem

If commit SHA is mentioned in the uppercase form, then it's not detected by markdown parser and not converted into the link to a commit.

Solution

Use case-insensitive comparison for commit SHAs.

References

• Uppercase git hashes are not transformed into l... (#453996 - closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Visit a project
2. Copy the last commit SHA from the repository (for example, 7a926a0c)
3. Create an issue and mention commit SHAs in both lowercase and uppercase formats (7a926a0c and 7A926A0C)
4. You should see both replaced by a link to the mentioned commit page

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #453996 (closed)