Update migration

Signed-off-by: methylDragon <methylDragon@gmail.com>

Migration.md

@@ -5,17 +5,19 @@ Deprecated code produces compile-time warnings. These warning serve as
 notification to users that their code should be upgraded. The next major
 release will remove the deprecated code.
 
-## Ignition Launch 2.2.2
-
-- Environment variable `IGN_LAUNCH_CONFIG_PATH` started to be treated as a path
-  list (colon-separated on Linux, semicolon-separated on Windows). Before, only
-  a single path could be set here, and setting a path list would break the whole
-  launch file lookup functionality.
+## Ignition Launch 5.X to 6.X
 
 - The `ignition` namespace is deprecated and will be removed in future versions.
   Use `gz` instead.
 
 - Header files under `ignition/...` are deprecated and will be removed in future versions.
   Use `gz/...` instead.
 
+## Ignition Launch 2.2.2
+
+- Environment variable `GZ_LAUNCH_CONFIG_PATH` started to be treated as a path
+  list (colon-separated on Linux, semicolon-separated on Windows). Before, only
+  a single path could be set here, and setting a path list would break the whole
+  launch file lookup functionality.
+
 ## Ignition Launch 0.X to N.M