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/compiler/optimizing/optimizing_unit_test.h b/compiler/optimizing/optimizing_unit_test.h
index 9aba912..e90c30d 100644
--- a/compiler/optimizing/optimizing_unit_test.h
+++ b/compiler/optimizing/optimizing_unit_test.h
@@ -161,7 +161,7 @@
 
 // An alias for the empty string used to make it clear that a line is
 // removed in a diff.
-static const std::string removed = "";
+static const std::string removed = "";  // NOLINT [runtime/string] [4]
 
 // Naive patch command: apply a diff to a string.
 inline std::string Patch(const std::string& original, const diff_t& diff) {