`Programming exercises`: Fix git-diff gutter width being too narrow for large files

[Hialus]

Checklist

General

• [x] I tested all changes and their related features with all corresponding user types on a test server.
• [x] This is a small issue that I tested locally and was confirmed by another developer on a test server.
• [x] Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• [x] I chose a title conforming to the naming conventions for pull requests.

Client

• [x] I followed the coding and design guidelines and ensured that the layout is responsive.
• [x] Following the theming guidelines, I specified colors only in the theming variable files and checked that the changes look consistent in both the light and the dark theme.
• [x] I added multiple integration tests (Jest) related to the features (with a high test coverage), while following the test guidelines.
• [x] I added authorities to all new routes and checked the course groups for displaying navigation elements (links, buttons).
• [x] I documented the TypeScript code using JSDoc style.
• [x] I added multiple screenshots/screencasts of my UI changes.
• [x] I translated all newly inserted strings into English and German.

Motivation and Context

On the live server I noticed that the line counter for the git-diff view was sometimes completely wrong and only displayed a single number like "9" for every line.

Description

This was caused by the gutter being too narrow and therefore only displaying the first number of the line counter (e.g. 9 for 92 and 1 for 120). This was in turn caused by an unnecessary addition, which I removed.

Steps for Testing

Prerequisites:

• 1 Instructor
• 1 Programming Exercise

1. Log in to Artemis
2. You need to create a long file in the programming exercise template and solution repos with the only changes between the two being in the double- or triple-digit range
3. Check that the git-diff view has the correct line numbers for this file.

Review Progress

Code Review

• [x] Review 1
• [x] Review 2

Manual Tests

• [x] Test 1
• [x] Test 2

Test Coverage

Unchanged