Clarify one PR for workflow

Author: mlfbrown

docs/assignments/hw4-25.md

@@ -185,6 +185,8 @@ Please provide a link to your merged commit.
 
 ### 8. Create a continuous integration pipeline to run your test cases
 
+*This is a group exercise. Only one person should PR the workflow file, and others should review.*
+
 To ensure the quality of our codebase, we want to make sure that your code passes all its test cases after every checkin. If the tests fail, we should reject the checkin.
 
 To setup our CI workflow, first, create a workflows subdirectory in .github. Then create a new file called ci.yml in workflows/.