Update predefined variables test for removed variables

The gitlab predefined variables > should not have new variables test currently assumes any variable in the table still exists. With GitLab 14, a variable was removed (#33 (closed)), but GitLab left the value in the table and updated it to indicate the variable was removed. See job #1365117621 failed for 332ddedf.

Update logic in the test to assume any value whose description field starts with "Removed".