.gitattributes does not handle -diff properly in UI

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Summary

-diff option is not working and not suppressing difference in UI when applied in .gitattributes file.

Note: git CLI works fine with this settings, it's just our UI is not using .gitattributes

Steps to reproduce

1. Create a repo with README
2. Create a new branch ("test")
3. Add the .gitattributes file with the following content on "test" branch

   # cat .gitattributes 
   ignoreme.txt -diff

4. Add the "ignoreme.txt" file on "test" branch

   # cat ignoreme.txt 
   first line
   this must be ignored by diff

5. Push the changes to the branch "test"
6. Observe with CLI git that the diff is suppressed:

   git diff main
   diff --git a/.gitattributes b/.gitattributes
   index e69de29..d2200ca 100644
   --- a/.gitattributes
   +++ b/.gitattributes
   @@ -0,0 +1 @@
   +ignoreme.txt -diff
   diff --git a/ignoreme.txt b/ignoreme.txt
   index 6cc3bfa..d0a2c51 100644
   Binary files a/ignoreme.txt and b/ignoreme.txt differ

7. Go to GL UI and compare the diff there (or create an MR and check the diff). This will show full content of the ignoreme.txt file and will not suppress the diff

What is the current bug behavior?

Diff of a file mentioned in .gitattributes with flag -diff is not suppressed in the UI

What is the expected correct behavior?

Diff is hidden in the UI "diff" view

Results of GitLab environment info

Expand for output related to GitLab environment info

```
sudo gitlab-rake gitlab:env:info

System information
System:		Ubuntu 20.04
Proxy:		no
Current User:	git
Using RVM:	no
Ruby Version:	2.7.6p219
Gem Version:	3.1.6
Bundler Version:2.3.15
Rake Version:	13.0.6
Redis Version:	6.2.7
Sidekiq Version:6.4.2
Go Version:	unknown

GitLab information
Version:	15.4.6-ee
Revision:	4fc991ae59a
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	PostgreSQL
DB Version:	13.8
URL:		https://gitlab-3.26.115.161.nip.io
HTTP Clone URL:	https://gitlab-3.26.115.161.nip.io/some-group/some-project.git
SSH Clone URL:	git@gitlab-3.26.115.161.nip.io:some-group/some-project.git
Elasticsearch:	no
Geo:		no
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers: 

GitLab Shell
Version:	14.10.0
Repository storage paths:
- default: 	/var/opt/gitlab/git-data/repositories
GitLab Shell path:		/opt/gitlab/embedded/service/gitlab-shell
```

Possible fixes