Rename getCurrentUser to getUser

It is never ambiguous to say "User" instead of "CurrentUser". Save
some typing.

Change-Id: I03a051f1fd3758ba63749cded20a7c135b6cf58a

gerrit-server/src/main/java/com/google/gerrit/server/git/EmailMerge.java

@@ -96,7 +96,7 @@ public class EmailMerge implements Runnable, RequestContext {
   }
 
   @Override
-  public CurrentUser getCurrentUser() {
+  public CurrentUser getUser() {
     throw new OutOfScopeException("No user on email thread");
   }