fix migration reversal code

Author: deer-wmde

database/migrations/2025_05_19_142457_add_monthly_user_count_to_wiki_daily_metrics_table.php

@@ -22,7 +22,9 @@ public function up(): void
      */
     public function down(): void
     {
-        Schema::table('wiki_daily_metric', function (Blueprint $table) {
+        Schema::table('wiki_daily_metrics', function (Blueprint $table) {
+            $table->dropColumn('monthly_casual_users');
+            $table->dropColumn('monthly_active_users');
         });
     }
 };