ci/linux/ffmpeg/oapv: drop -ffat-lto-objects

it was taken from:
<https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=openapv-git>
but it is unsure what is the advantage, see:
<https://stackoverflow.com/questions/13799452/what-is-the-difference-in-gcc-between-lto-and-fat-lto-objects>

see gcc man page for definition -> no real advantage observed when used

Author: MartinPulec

.github/scripts/Linux/install_ffmpeg.sh

@@ -69,7 +69,6 @@ install_nv_codec_headers() (
 
 install_oapv() (
         git clone --depth 1 https://github.com/AcademySoftwareFoundation/openapv.git
-        export CFLAGS='-ffat-lto-objects'
         cmake -B openapv/build -S openapv \
                 -DCMAKE_BUILD_TYPE=Release
         cmake --build openapv/build --parallel "$(nproc)"