Fix theos cache

Author: Pe13

.github/workflows/build.yml

@@ -144,7 +144,7 @@ jobs:
       uses: actions/cache@v3
       with:
         path: ${{ github.workspace }}/theos
-        key: ${{ runner.os }}-${{ env.upstream_heads }}
+        key: ${{ env.upstream_heads }}
 
     - name: Prepare Theos
       uses: Randomblock1/theos-action@v1