third_party: update nghttp2 from 1.46.0 to 1.47.0

This will fix compilation on recent Archlinux. The issue is this distro
installs libbpf in base configuration and nghttp2 1.46.0 tries to
compile eBPF code if this library is present and failed if compiler is
gcc.

Closes #7292

NO_DOC=nghttp2 submodule bump
NO_TEST=nghttp2 submodule bump

changelogs/unreleased/gh-7292-fix-gcc-build-with-libbpf-installed.md

+## bugfix/build
+
+* Fix build failure with gcc if libpbf is installed. (gh-7292)

nghttp2 @ 5fc0cfd8

-Subproject commit 4483fdae7ae777960e2d95bcb22bcca05bee36f9
+Subproject commit 5fc0cfd89876c94e8f1edc59716363dbcdbbbe38