fix(workflow): use tag for srtool image

Author: DylanVerstraete

.github/workflows/build_runtime.yaml

@@ -24,7 +24,7 @@ jobs:
         id: srtool_build
         uses: chevdor/srtool-actions@v0.6.0
         with:
-          image: paritytech/srtool:1.66.1
+          tag: 1.66.1
           workdir: '${{ github.workspace }}/substrate-node'
           package: tfchain-runtime
           runtime_dir: runtime