GitHub: remove duplicate caching

Turns out that actions/setup-go starting with @v4 also adds caching.
With that, our cache size on disk has almost doubled, leading to the
GitHub runner running out of space in certain situation.
We fix that by disabling the automated caching since we already have our
own, custom-tailored version.

.github/actions/setup-go/action.yml

@@ -22,6 +22,7 @@ runs:
       uses: actions/setup-go@v5
       with:
         go-version: '${{ inputs.go-version }}'
+        cache: 'false'
 
     - name: go cache
       if: ${{ inputs.use-build-cache == 'yes' }}
@@ -44,7 +45,7 @@ runs:
 
     - name: go module cache
       if: ${{ inputs.use-build-cache == 'no' }}
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         # Just the module download cache.
         path: |