Bump actions/upload-artifact from 4 to 6

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v4...v6)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/c_actions.yml

@@ -68,21 +68,21 @@ jobs:
       working-directory: gfe_integration_tests
 
     - name: Upload Fec binaries
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@v6
       with:
         name: fec_binaries
         path: SpiNNFrontEndCommon/spinn_front_end_common/common_model_binaries/*.aplx
         retention-days: 5
 
     - name: Upload test_extra_monitor binaries
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@v6
       with:
         name: test_extra_monitor_binary
         path: gfe_integration_tests/test_extra_monitor/*.aplx
         retention-days: 5
 
     - name: Upload log.sqlite3s
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@v6
       with:
         name: logs.sqlite3
         path: logs.sqlite3