purge-old-deployments: Remove an unnecessary check.

Deployments whose name is not in the format of a timestamp are
always included in the `recent_deployments` and are not deleted,
hence we don't need to check for them explicitly.

scripts/purge-old-deployments

@@ -1,6 +1,5 @@
 #!/usr/bin/env python3
 import argparse
-import datetime
 import os
 import subprocess
 import sys
@@ -42,14 +41,11 @@ def get_deployments_to_be_purged(recent_deployments):
                            for deployment in os.listdir(DEPLOYMENTS_DIR)])
     deployments_to_purge = set()
     for deployment in all_deployments:
+        # Deployments whose name is not in the format of a timestamp are
+        # always included in the recent_deployments and are not deleted.
         if not os.path.isdir(deployment):
             # Skip things like uwsgi sockets.
             continue
-        try:
-            datetime.datetime.strptime(deployment, TIMESTAMP_FORMAT)
-        except ValueError:
-            # Never purge deployments whose name is not in the format of a timestamp.
-            continue
         if deployment not in recent_deployments:
             deployments_to_purge.add(deployment)
     return deployments_to_purge