Remove the (now-nonexistent) battor agent target from a whitelist

It looks like this file has * listed as its owner, so it doesn't need
any specific owner review.

Bug: 859514
Cq-Include-Trybots: luci.chromium.try:linux_chromium_dbg_ng
Change-Id: I9afd700a6a36f00b5fb46847fbc5d01d08646db8
Reviewed-on: https://chromium-review.googlesource.com/1169437
Commit-Queue: Charlie Andrews <charliea@chromium.org>
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#582236}

build/check_gn_headers_whitelist.txt

@@ -344,7 +344,6 @@ third_party/woff2/src/port.h
 third_party/yasm/source/config/linux/config.h
 third_party/yasm/source/config/linux/libyasm-stdint.h
 third_party/zlib/contrib/minizip/crypt.h
-tools/battor_agent/battor_protocol_types.h
 tools/gn/ordered_set.h
 tools/ipc_fuzzer/message_lib/all_message_null_macros.h
 ui/app_list/app_list_export.h