Update build.yml

Bump actions to latest version.

Author: aaaronic

.github/workflows/build.yml

@@ -8,7 +8,7 @@ jobs:
       - name: Build
         run: docker run --rm -v ${{ github.workspace }}:/gba aaaronic/gba-compiler:1.2
       - name: Upload Project.gba
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: Project.gba
           path: ${{ github.workspace }}/Project.gba