Rename exercises dir

Name it instead "topics" so it won't be
strange if some topics included "exercises" directory.

topics/cicd/remove_jobs.md

@@ -0,0 +1,10 @@
+### Jenkins - Remove Jobs
+
+#### Objective 
+
+Learn how to write a Jenkins script to remove Jenkins jobs
+
+#### Instructions
+
+1. Create three jobs called: test-job, test2-job and prod-job
+2. Write a script to remove all the jobs that include the string "test"