Remove Http2String wrapper for std::string.

gfe-relnote: n/a, no functional change.
PiperOrigin-RevId: 263816460
Change-Id: I4f365540414e6a3d78fd00ce6b39a4cdd4c14140

http2/hpack/huffman/hpack_huffman_encoder.h

diff --git a/http2/hpack/huffman/hpack_huffman_encoder.h b/http2/hpack/huffman/hpack_huffman_encoder.h
index bf6b1b2..247aaff 100644
--- a/http2/hpack/huffman/hpack_huffman_encoder.h
+++ b/http2/hpack/huffman/hpack_huffman_encoder.h
@@ -9,9 +9,9 @@
 // table.
 
 #include <cstddef>  // For size_t
+#include <string>
 
 #include "net/third_party/quiche/src/http2/platform/api/http2_export.h"
-#include "net/third_party/quiche/src/http2/platform/api/http2_string.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_string_piece.h"
 
 namespace http2 {
@@ -33,7 +33,7 @@
 // the beginning of this function.  This allows reusing the same string object
 // across multiple invocations.
 HTTP2_EXPORT_PRIVATE void HuffmanEncode(Http2StringPiece plain,
-                                        Http2String* huffman);
+                                        std::string* huffman);
 
 }  // namespace http2