ci: update upload-artifact and download-artifact actions to v4 (#4063)

- **PR Description**

v3 of `actions/upload-artifact` and `actions/download-artifact` will be
fully deprecated by **5 December 2024**. Jobs that are scheduled to run
during the brownout periods will also fail. See:

1.
https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/
2.
https://github.blog/changelog/2024-11-05-notice-of-breaking-changes-for-github-actions/

- **Please check if the PR fulfills these requirements**

* [x] Cheatsheets are up-to-date (run `go generate ./...`)
* [x] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [ ] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [ ] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] If a new UserConfig entry was added, make sure it can be
hot-reloaded (see
[here](https://github.com/jesseduffield/lazygit/blob/master/docs/dev/Codebase_Guide.md#using-userconfig))
* [ ] Docs have been updated if necessary
* [x] You've read through your own file changes for silly mistakes etc

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.github/workflows/ci.yml

@@ -39,7 +39,7 @@ jobs:
           mkdir -p /tmp/code_coverage
           go test ./... -short -cover -args "-test.gocoverdir=/tmp/code_coverage"
       - name: Upload code coverage artifacts
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: coverage-unit-${{ matrix.os }}-${{ github.run_id }}
           path: /tmp/code_coverage
@@ -100,7 +100,7 @@ jobs:
           mkdir -p /tmp/code_coverage
           ./scripts/run_integration_tests.sh
       - name: Upload code coverage artifacts
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: coverage-integration-${{ matrix.git-version }}-${{ github.run_id }}
           path: /tmp/code_coverage
@@ -200,7 +200,7 @@ jobs:
           go-version: 1.22.x
 
       - name: Download all coverage artifacts
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           path: /tmp/code_coverage