feat: drop the 2.8 columns, moves and aliases kept for a downgrade

drizzle/mysql/meta/_journal.json

@@ -463,6 +463,20 @@
       "when": 1790742086934,
       "tag": "0065_ambiguous_agent_zero",
       "breakpoints": true
+    },
+    {
+      "idx": 66,
+      "version": "5",
+      "when": 1791209297104,
+      "tag": "0066_retire_2_8_columns",
+      "breakpoints": true
+    },
+    {
+      "idx": 67,
+      "version": "5",
+      "when": 1791209311841,
+      "tag": "0067_external_session_ref",
+      "breakpoints": true
     }
   ]
 }