Fix cpplint's whitespace warnings.

Change-Id: I16b69d773e59b49e8e30227b5aa5cb1959a8930f
diff --git a/src/base64.cc b/src/base64.cc
index 4966314..1709946 100644
--- a/src/base64.cc
+++ b/src/base64.cc
@@ -73,4 +73,4 @@
   return dst.release();
 }
 
-};
+}  // namespace art