fix fbcode-builder build with googletest-1.11

Reviewed By: ahornby

Differential Revision: D34030118

fbshipit-source-id: 2229527eebb147a9c2eea90be78ab72e63e2fe3f

folly/experimental/crypto/test/LtHashTest.cpp

@@ -57,12 +57,14 @@ struct IsLtHash<LtHash<B, N>> {
 
 } // namespace
 
+namespace folly::crypto {
 // Needed so an EXPECT_EQ() or EXPECT_NE() failure prints the LtHash checksum.
 template <std::size_t B, std::size_t N>
 static std::ostream& operator<<(std::ostream& os, const LtHash<B, N>& h) {
   os << toHex(*h.getChecksum());
   return os;
 }
+} // namespace folly::crypto
 
 // Note: the template parameter H must be an instance of LtHash<B, N> for some
 // valid B and N.