chore(build): Update cloudbuild.yaml file (#482)

Remove the $REPO_NAME variable from the cloudbuild.yaml file; this is being used
to decide the name of the image to push which will not always correspond to the
image name. In particular, if we start publishing both alpine and ubuntu images
we'll want the image name to have a suffix reflecting that.

cloudbuild.yaml

@@ -4,10 +4,10 @@ steps:
   entrypoint: "bash"
   args: ["-c", "./gradlew igor-web:installDist -x test"]
 - name: gcr.io/cloud-builders/docker
-  args: ["build", "-t", "gcr.io/$PROJECT_ID/$REPO_NAME:$TAG_NAME", "-f", "Dockerfile.slim", "."]
+  args: ["build", "-t", "gcr.io/$PROJECT_ID/igor:$TAG_NAME", "-f", "Dockerfile.slim", "."]
   env: ["GRADLE_USER_HOME=/gradle_cache/.gradle"]
 images:
-- gcr.io/$PROJECT_ID/$REPO_NAME:$TAG_NAME
+- gcr.io/$PROJECT_ID/igor:$TAG_NAME
 timeout: 3600s
 options:
   machineType: N1_HIGHCPU_8