Increase merge request diff file size limit for default toggle opening

• Currently, in a merge request, a file diff is by default toggled opened if the file size is under 10 KB. https://gitlab.com/gitlab-org/gitlab-ce/issues/31055#note_27598227.
• This issue changes that limit to 100 KB, which is the same as the global limit. (https://gitlab.com/gitlab-org/gitlab-ce/issues/31055#note_29029553).
• This will help improve the usability of the merge request diff, especially for our blog posts.
• Note the implementation should not remove the limit. The limit should just be changed to 100 KB. In a future issue, the limit will be removed altogether, and the system will just fall back to the global value.