Bump actions/upload-artifact from 6 to 7

Bumps [actions/upload-artifact](https://github.com/actions/upload-artifact) from 6 to 7.
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v6...v7)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/build-natives.yml

@@ -41,7 +41,7 @@ jobs:
                 unzip -j chrome-win.zip chrome-win/libGLESv2.dll -d artifacts/x64
 
             - name: Upload Artifacts
-              uses: actions/upload-artifact@v6
+              uses: actions/upload-artifact@v7
               with:
                 name: Natives-Windows
                 path: ./artifacts
@@ -68,7 +68,7 @@ jobs:
                 lipo -thin arm64 lib/libSDL2-2.0.0.dylib -output ../../artifacts/arm64/SDL2.dylib
 
             - name: Upload Artifacts
-              uses: actions/upload-artifact@v6
+              uses: actions/upload-artifact@v7
               with:
                 name: Natives-MacOS
                 path: ./artifacts
@@ -102,7 +102,7 @@ jobs:
                 cp lib/libSDL2.so ../artifacts/x64/SDL2.so
 
             - name: Upload Artifacts
-              uses: actions/upload-artifact@v6
+              uses: actions/upload-artifact@v7
               with:
                 name: Natives-Linux(x64)
                 path: ./artifacts
@@ -126,7 +126,7 @@ jobs:
                 cp lib/libSDL2.so ../artifacts/arm64/SDL2.so
 
             - name: Upload Artifacts
-              uses: actions/upload-artifact@v6
+              uses: actions/upload-artifact@v7
               with:
                 name: Natives-Linux(arm64)
                 path: ./artifacts

.github/workflows/build-nuget.yml

@@ -83,7 +83,7 @@ jobs:
                 nuget pack OpenRA-SDL2-CS.nuspec -OutputDirectory ./nuget -version ${{ env.PACKAGE_VERSION }}
 
             - name: Upload NuGet package to Artifacts
-              uses: actions/upload-artifact@v6
+              uses: actions/upload-artifact@v7
               with:
                 name: NuGet Package ${{ env.PACKAGE_VERSION }}
                 path: ./nuget

.github/workflows/build-sdl2cs.yml

@@ -27,7 +27,7 @@ jobs:
                 dotnet build SDL2-CS.sln
 
             - name: Upload Artifacts
-              uses: actions/upload-artifact@v6
+              uses: actions/upload-artifact@v7
               with:
                 name: SDL2-CS
                 path: ./bin