ref(migrations): Drop {next,last}_checkin columns (db op) (#49256)

Follow up to https://github.com/getsentry/sentry/pull/49132

---------

Co-authored-by: getsantry[bot] <66042841+getsantry[bot]@users.noreply.github.com>

migrations_lockfile.txt

@@ -6,5 +6,5 @@ To resolve this, rebase against latest master and regenerate your migration. Thi
 will then be regenerated, and you should be able to merge without conflicts.
 
 nodestore: 0002_nodestore_no_dictfield
-sentry: 0444_remove_next_checkin_last_checkin_from_monitor
+sentry: 0445_drop_deprecated_monitor_next_last_checkin_db_op
 social_auth: 0001_initial

src/sentry/migrations/0445_drop_deprecated_monitor_next_last_checkin_db_op.py

@@ -0,0 +1,42 @@
+# Generated by Django 2.2.28 on 2023-05-16 21:28
+
+from django.db import migrations
+
+from sentry.new_migrations.migrations import CheckedMigration
+
+
+class Migration(CheckedMigration):
+    # This flag is used to mark that a migration shouldn't be automatically run in production. For
+    # the most part, this should only be used for operations where it's safe to run the migration
+    # after your code has deployed. So this should not be used for most operations that alter the
+    # schema of a table.
+    # Here are some things that make sense to mark as dangerous:
+    # - Large data migrations. Typically we want these to be run manually by ops so that they can
+    #   be monitored and not block the deploy for a long period of time while they run.
+    # - Adding indexes to large tables. Since this can take a long time, we'd generally prefer to
+    #   have ops run this and not block the deploy. Note that while adding an index is a schema
+    #   change, it's completely safe to run the operation after the code has deployed.
+    is_dangerous = False
+
+    dependencies = [
+        ("sentry", "0444_remove_next_checkin_last_checkin_from_monitor"),
+    ]
+
+    operations = [
+        migrations.SeparateDatabaseAndState(
+            database_operations=[
+                migrations.RunSQL(
+                    """
+                    ALTER TABLE "sentry_monitor" DROP COLUMN "last_checkin";
+                    ALTER TABLE "sentry_monitor" DROP COLUMN "next_checkin";
+                    """,
+                    reverse_sql="""
+                    ALTER TABLE "sentry_monitor" ADD COLUMN "last_checkin" timestamp with time zone NULL;
+                    ALTER TABLE "sentry_monitor" ADD COLUMN "next_checkin" timestamp with time zone NULL;
+                    """,
+                    hints={"tables": ["sentry_monitor"]},
+                )
+            ],
+            state_operations=[],
+        )
+    ]