more accurate key deletion

lib/gitlab_keys.rb

@@ -28,7 +28,7 @@ class GitlabKeys
   end
 
   def rm_key
-    cmd = "sed -i '/#{@key_id}/d' #{auth_file}"
+    cmd = "sed -i '/shell #{@key_id}/d' #{auth_file}"
     system(cmd)
   end
 end