Delete some old code related to reencryption

We've moved past the point where this code would still be live.

awx/main/migrations/0015_v330_blank_start_args.py

@@ -5,10 +5,6 @@ from __future__ import unicode_literals
 # Django
 from django.db import migrations
 
-# AWX
-from awx.main.migrations import _migration_utils as migration_utils
-from awx.main.migrations._reencrypt import blank_old_start_args
-
 
 class Migration(migrations.Migration):
 
@@ -17,6 +13,8 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
-        migrations.RunPython(migration_utils.set_current_apps_for_migrations, migrations.RunPython.noop),
-        migrations.RunPython(blank_old_start_args, migrations.RunPython.noop),
+        # This list is intentionally empty.
+        # Tower 3.3 included several data migrations that are no longer
+        # necessary (this list is now empty because Tower 3.3 is past EOL and
+        # cannot be directly upgraded to modern versions)
     ]

awx/main/migrations/_reencrypt.py

@@ -1,26 +0,0 @@
-import logging
-
-from awx.conf.migrations._reencrypt import (
-    decrypt_field,
-)
-
-logger = logging.getLogger('awx.main.migrations')
-
-__all__ = []
-
-
-def blank_old_start_args(apps, schema_editor):
-    UnifiedJob = apps.get_model('main', 'UnifiedJob')
-    for uj in UnifiedJob.objects.defer('result_stdout_text').exclude(start_args='').iterator():
-        if uj.status in ['running', 'pending', 'new', 'waiting']:
-            continue
-        try:
-            args_dict = decrypt_field(uj, 'start_args')
-        except ValueError:
-            args_dict = None
-        if args_dict == {}:
-            continue
-        if uj.start_args:
-            logger.debug('Blanking job args for %s', uj.pk)
-            uj.start_args = ''
-            uj.save()