Use general headline for migration hint

mbrodala · web-flow · commit d38ea0d9f20a · 2020-12-23T15:47:09.000+01:00
diff --git a/README.md b/README.md
@@ -656,7 +656,7 @@ services:
         # ...
 ```
 
-## Migrating from v2
+## Migrating from older image versions
 
 Check the [migration notes](MIGRATING.md).
 
