update version to rc12

Author: timfel

mx.graalpython/suite.py

@@ -8,7 +8,7 @@
     "name": "graalpython",
     "versionConflictResolution": "latest",
 
-    "version": "1.0.0-rc11",
+    "version": "1.0.0-rc12",
     "release": False,
     "groupId": "org.graalvm.graalpython",
     "url": "http://www.graalvm.org/",