Increase the default `max_attachment_size` to `100` to match GitLab.com
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The following discussion from !103978 should be addressed:
- [ ] @phikai started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/103978#note_1171450327):
> Settings for GitLab.com and the default settings for GitLab should match. We'll need a follow up to change the default settings.
## Proposal
The `max_attachment_size` default value should be updated for all of GitLab to the new 100MB value that GitLab.com is going to use.
issue