docs: add instructions for migration from 23.09 to 24.03 (#1997)

MIGRATION.md

@@ -6,6 +6,9 @@ Backend.AI Migration Guide
 * The migration should be done while the managers and agents are shut down.
 * This guide only describes additional steps to follow other than the code/package upgrades.
 
+# 23.09 to 24.03
+* DB revision must be downgraded to 85615e005fa3 **before** initiating Backend.AI manager Python package upgrade
+
 # 23.03 to 23.09
 * webserver configuration scheme updated
   - `webserver`, `logging` and `debug` categories added, with all of those marked as required.

README.md

@@ -268,11 +268,11 @@ or native SSH connection to kernels via our client SDK or desktop apps.
 Python Version Compatibility
 ----------------------------
 
-| Backend.AI Core Version | Compatible Python Version |
-|:-----------------------:|:-------------------------:|
-| 23.03.x / 23.09.x       | 3.11.x                    |
-| 22.03.x / 22.09.x       | 3.10.x                    |
-| 21.03.x / 21.09.x       | 3.8.x                     |
+| Backend.AI Core Version     | Compatible Python Version |
+|:---------------------------:|:-------------------------:|
+| 23.03.x / 23.09.x / 24.03.x | 3.11.x                    |
+| 22.03.x / 22.09.x           | 3.10.x                    |
+| 21.03.x / 21.09.x           | 3.8.x                     |
 
 
 License