Remove non-existing headers from the build

ppapi/c/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # These are just headers.
 source_set("c") {
   sources = [
     "pp_array_output.h",
     "pp_bool.h",
     "pp_codecs.h",
@@ skipping 38 matching lines @@
     "ppb_media_stream_video_track.h",
     "ppb_message_loop.h",
     "ppb_messaging.h",
     "ppb_mouse_cursor.h",
     "ppb_mouse_lock.h",
     "ppb_net_address.h",
     "ppb_network_list.h",
     "ppb_network_monitor.h",
     "ppb_network_proxy.h",
     "ppb_opengles2.h",
-    "ppb_ppb_vpn_provider.h",
     "ppb_tcp_socket.h",
     "ppb_text_input_controller.h",
     "ppb_udp_socket.h",
     "ppb_url_loader.h",
     "ppb_url_request_info.h",
     "ppb_url_response_info.h",
     "ppb_var.h",
     "ppb_var_array.h",
     "ppb_var_array_buffer.h",
     "ppb_var_dictionary.h",
@@ skipping 96 matching lines @@
 
     # Trusted interfaces.
     "trusted/ppb_broker_trusted.h",
     "trusted/ppb_browser_font_trusted.h",
     "trusted/ppb_char_set_trusted.h",
     "trusted/ppb_file_chooser_trusted.h",
     "trusted/ppb_url_loader_trusted.h",
     "trusted/ppp_broker.h",
   ]
 }