clang-format-6.0 bump fixes

The bump to use clang-format-6.0 now reports these issues.

Change-Id: Ice27766e161356f08c98923a256a98af787ac8a2
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/mapbox/variant.hpp b/mapbox/variant.hpp
index 37c736d..46db853 100644
--- a/mapbox/variant.hpp
+++ b/mapbox/variant.hpp
@@ -1058,7 +1058,7 @@
     return V::binary_visit(v0, v1, std::forward<F>(f));
 }
 
-    // getter interface
+// getter interface
 
 #ifdef HAS_EXCEPTIONS
 template <typename ResultType, typename T>