CI Linux FFmpeg: do not build own libx264

added by the commit f3003ed1

For the original reason it is no longer needed (the higher bit depth
x264 is already included in distro repositories). Anyways, the version
of libx264, that will be installed, is taken from ppa:savoury1/vlc3,
anyways (newer one).

.github/scripts/Linux/download_build_ffmpeg.sh

@@ -55,7 +55,6 @@ if [ "$(lsb_release -rs)" = 20.04 ]; then
         git am -3 "$GITHUB_WORKSPACE/.github/scripts/Linux/ffmpeg-patches/0001-removed-bits-incompatible-with-old-vaapi.patch-noauto"
 fi
 install_aom
-( git clone --depth 1 http://git.videolan.org/git/x264.git && cd x264 && ./configure --disable-static --enable-shared && make -j "$(nproc)" && sudo make install || exit 1 )
 install_libvpx
 install_nv_codec_headers
 install_onevpl

.github/scripts/Linux/install_ffmpeg.sh

@@ -2,7 +2,6 @@
 
 cd /var/tmp/ffmpeg
 ( cd libvpx && sudo make install )
-( cd x264 && sudo make install )
 ( cd nv-codec-headers && sudo make install )
 ( cd aom/build && sudo cmake --install . )
 sudo cmake --install SVT-AV1/Build

.github/scripts/Linux/prepare.sh

@@ -53,9 +53,7 @@ sudo add-apt-repository ppa:savoury1/vlc3 # new x265
 ffmpeg_build_dep=$(get_build_deps_excl ffmpeg 'libzmq3-dev\|libsdl2-dev')
 # shellcheck disable=SC2086 # intentional
 sudo apt install $ffmpeg_build_dep libdav1d-dev libde265-dev
-sudo apt-get -y remove 'libavcodec*' 'libavutil*' 'libswscale*' libvpx-dev 'libx264*' nginx
-# own x264 build
-sudo apt --no-install-recommends install asciidoc xmlto
+sudo apt-get -y remove 'libavcodec*' 'libavutil*' 'libswscale*' libvpx-dev nginx
 
 sudo apt install qtbase5-dev