8193819: Error message when module does not have a ModuleMainClass attribute is confusing

[Alan Bateman]

There's a typo in the launcher resource used for the error message when 
`java -m` fails because the module doesn't have a main class. The name 
of the attribute is "ModuleMainClass", not "MainClass". Trivial change.

-Alan


diff --git 
a/src/java.base/share/classes/sun/launcher/resources/launcher.properties 
b/src/java.base/share/classes/sun/launcher/resources/launcher.properties
--- a/src/java.base/share/classes/sun/launcher/resources/launcher.properties
+++ b/src/java.base/share/classes/sun/launcher/resources/launcher.properties
@@ -220,7 +220,7 @@
      Error: The JavaFX launchApplication method has the wrong 
signature, it\n\
      must be declared static and return a value of type void
  java.launcher.module.error1=\
-    module {0} does not have a MainClass attribute, use -m 
<module>/<main-class>
+    module {0} does not have a ModuleMainClass attribute, use -m 
<module>/<main-class>
  java.launcher.module.error2=\
      Error: Could not find or load main class {0} in module {1}
  java.launcher.module.error3=\