Remove Http2String wrapper for std::string.

gfe-relnote: n/a, no functional change.
PiperOrigin-RevId: 263816460
Change-Id: I4f365540414e6a3d78fd00ce6b39a4cdd4c14140
diff --git a/http2/hpack/tools/hpack_block_builder_test.cc b/http2/hpack/tools/hpack_block_builder_test.cc
index a7b8064..bba363f 100644
--- a/http2/hpack/tools/hpack_block_builder_test.cc
+++ b/http2/hpack/tools/hpack_block_builder_test.cc
@@ -96,7 +96,7 @@
     // 0x0000:  8286 8441 0f77 7777 2e65 7861 6d70 6c65  ...A.www.example
     // 0x0010:  2e63 6f6d                                .com
 
-    const Http2String expected =
+    const std::string expected =
         Http2HexDecode("828684410f7777772e6578616d706c652e636f6d");
     EXPECT_EQ(expected, b.buffer());
   }
@@ -127,7 +127,7 @@
     // 0x0000:  8286 8441 8cf1 e3c2 e5f2 3a6b a0ab 90f4  ...A......:k....
     // 0x0010:  ff                                       .
 
-    const Http2String expected =
+    const std::string expected =
         Http2HexDecode("828684418cf1e3c2e5f23a6ba0ab90f4ff");
     EXPECT_EQ(expected, b.buffer());
   }