[Feature:Autograding] Fixed a typo in the workflow file (#51)

### Please check if the PR fulfills these requirements:

* [ ] Tests for the changes have been added/updated (if possible)
* [ ] Documentation has been updated/added if relevant

### What is the current behavior?
<!-- List issue if it fixes/closes/implements one using the "Fixes
#<number>" or "Closes #<number>" syntax -->
There is a duplicate `Docker Build and Push` workflow

### What is the new behavior?
There will no longer be a duplicate `Docker Build and Push` workflow

### Other information?
<!-- Is this a breaking change? -->
<!-- How did you test -->

.github/workflows/docker-build-pr.yml

@@ -1,4 +1,4 @@
-name: Docker Build and Push
+name: Docker Build PR
 
 on:
   pull_request: