Fix non-noise cpplint errors in //crypto.

crypto/scoped_test_system_nss_key_slot.h

Index: crypto/scoped_test_system_nss_key_slot.h
diff --git a/crypto/scoped_test_system_nss_key_slot.h b/crypto/scoped_test_system_nss_key_slot.h
index eb8fbc97a8feb2e2d8560db9a5f1712dae8ccba9..ae9b2cd8a5b7ff8feeacae8152622eeb39a9a913 100644
--- a/crypto/scoped_test_system_nss_key_slot.h
+++ b/crypto/scoped_test_system_nss_key_slot.h
@@ -27,7 +27,7 @@ class ScopedTestNSSDB;
 // At most one instance of this helper must be used at a time.
 class CRYPTO_EXPORT ScopedTestSystemNSSKeySlot {
  public:
-  explicit ScopedTestSystemNSSKeySlot();
+  ScopedTestSystemNSSKeySlot();
   ~ScopedTestSystemNSSKeySlot();
 
   bool ConstructedSuccessfully() const;