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] <[email protected]>

Author: dependabot[bot]

.github/workflows/CI_build.yml

@@ -35,14 +35,14 @@ jobs:
 
     - name: Archive artifacts for x64
       if: matrix.build_platform == 'x64' && matrix.build_configuration == 'Release'
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@v6
       with:
           name: plugin_dll_x64
           path: NppCSharpPluginPack\bin\${{ matrix.build_configuration }}-x64\CSharpPluginPack.dll
 
     - name: Archive artifacts for x86
       if: matrix.build_platform == 'x86' && matrix.build_configuration == 'Release'
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@v6
       with:
           name: plugin_dll_x86
           path: NppCSharpPluginPack\bin\${{ matrix.build_configuration }}\CSharpPluginPack.dll