Invalidate after replace() succeeds

* So we don't do extra invalidations, and it is not possible to get an
  entry that is not valid but not yet replaced in the map.

Author: eregon

src/main/java/org/truffleruby/core/module/ModuleFields.java

@@ -788,8 +788,8 @@ private void newMethodVersion(String methodToInvalidate) {
             if (methodEntry == null) {
                 return;
             } else {
-                methodEntry.invalidate(rubyModule, methodToInvalidate);
                 if (methods.replace(methodToInvalidate, methodEntry, methodEntry.withNewAssumption())) {
+                    methodEntry.invalidate(rubyModule, methodToInvalidate);
                     return;
                 }
             }