Update readme to reflect new stable branch

Author: enebo

README.md

@@ -26,9 +26,10 @@ Versions are targeted at certain versions of Rails and live on their own branche
 | 60.x        | 6.0.x         | 60-stable | 9.2.7     | 8        |
 | 61.x        | 6.1.x         | 61-stable | 9.2.7     | 8        |
 | 70.x        | 7.0.x         | 70-stable | 9.3.0     | 8        |
-| 71.x        | 7.1.x         | master    | 9.4.3     | 8        |
+| 71.x        | 7.1.x         | 71-stable | 9.4.3     | 8        |
+| 72.x        | 7.2.x         | master    | 9.4.3     | 8        |
 
-Note: 71.x is still under development and not supported yet.
+Note: 72.x is still under development and not supported yet.
 
 Note that JRuby 9.1.x and JRuby 9.2.x are at end-of-life. We recommend Java 8
 at a minimum for all versions.