Fix release build

Author: Shillaker

.github/workflows/release.yml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: "Get the code"
         uses: actions/checkout@v2
@@ -31,6 +31,5 @@ jobs:
         uses: docker/build-push-action@v2
         with:
           push: true
-          file: docker/cpython.dockerfile
           context: .
           tags: faasm/cpython:${{ env.TAG_VERSION }}