.github/workflows: Bump the docker/build-push-action to the v2 version

Update the test-scripts.yml workflow and replace the
docker/build-push-action to use the v2 version.

These changes were made by following their upgrade from v1 to v2 guide:
- https://github.com/docker/build-push-action/blob/master/UPGRADE.md.

We only use this action currently to ensure that builds are successful
and don't push (or test against) the newly build container image.

Author: timflannagan

.github/workflows/test-scripts.yml

@@ -10,14 +10,14 @@ on:
 jobs:
   image-build:
     runs-on: ubuntu-latest
-    steps: 
+    steps:
     - name: Check out the repo
       uses: actions/checkout@v2
     - name: Build the container image
-      uses: docker/build-push-action@v1
+      uses: docker/build-push-action@v2
       with:
-        repository: operator-framework/olm
-        dockerfile: ./Dockerfile
+        context: .
+        file: Dockerfile
         push: false
   run-local-minikube:
     runs-on: ubuntu-latest