Make proxygen http server header samples available (installed)

Summary:
Make proxygen http server header samples available (installed).
This diff enables to copy the header files from `fbcode/proxygen/httpserver/samples/*.h` to includes installed directory. Then dependencies of this lib can use them

MOQ (Media Over QUIC) depends on HQServer

Reviewed By: lnicco

Differential Revision: D57014991

fbshipit-source-id: 8a0c6210dc2512fc4b6ce3b5bf0f084366fb2047

third-party/proxygen/src/proxygen/httpserver/CMakeLists.txt

@@ -250,7 +250,6 @@ file(
     *.h
 )
 list(FILTER PROXYGEN_HTTPSERVER_HEADERS_TOINSTALL EXCLUDE REGEX tests/)
-list(FILTER PROXYGEN_HTTPSERVER_HEADERS_TOINSTALL EXCLUDE REGEX samples/)
 foreach(header ${PROXYGEN_HTTPSERVER_HEADERS_TOINSTALL})
     get_filename_component(header_dir ${header} DIRECTORY)
     install(FILES ${header} DESTINATION include/proxygen/httpserver/${header_dir})