cpplint: Cleanup errors

Cleanup errors from upstream cpplint in preparation
for moving art's cpplint fork to upstream tip-of-tree cpplint.

Test: cd art && mm
Bug: 68951293
Change-Id: I15faed4594cbcb8399850f8bdee39d42c0c5b956
diff --git a/runtime/class_table.h b/runtime/class_table.h
index 744c010..48129b1 100644
--- a/runtime/class_table.h
+++ b/runtime/class_table.h
@@ -41,9 +41,9 @@
 }  // namespace linker
 
 namespace mirror {
-  class Class;
-  class ClassLoader;
-  class Object;
+class Class;
+class ClassLoader;
+class Object;
 }  // namespace mirror
 
 // Each loader has a ClassTable