Ensure order of precedence in matching `main` branch in backports

.backportrc.json

@@ -3,7 +3,7 @@
   "targetBranchChoices" : [ "main", "8.4", "8.3", "8.2", "8.1", "8.0", "7.17", "6.8" ],
   "targetPRLabels" : [ "backport" ],
   "branchLabelMapping" : {
-    "^v(\\d+).(\\d+).\\d+(?:-(?:alpha|beta|rc)\\d+)?$" : "$1.$2",
-    "^v8.5.0$" : "main"
+    "^v8.5.0$" : "main",
+    "^v(\\d+).(\\d+).\\d+(?:-(?:alpha|beta|rc)\\d+)?$" : "$1.$2"
   }
 }