Drop WITH_X264 build option

The X264 support has never been implemented upstream. Let's drop
the non-existent WITH_X264 build option.

Related: https://github.com/FreeRDP/FreeRDP/issues/5698
Related: 112400ca66

freerdp.spec

@@ -1,9 +1,8 @@
-# Can be rebuilt with FFmpeg/H264 support enabled by passing "--with=ffmpeg",
-# "--with=x264" or "--with=openh264" to mock/rpmbuild; or by globally setting
-# these variables:
+# Can be rebuilt with FFmpeg/OpenH264 support enabled by passing
+# "--with=ffmpeg", or "--with=openh264" to mock/rpmbuild; or by globally
+# setting these variables:
 
 #global _with_ffmpeg 1
-#global _with_x264 1
 #global _with_openh264 1
 
 # Momentarily disable GSS support
@@ -175,7 +174,6 @@ find . -name "*.c" -exec chmod 664 {} \;
     -DWITH_SOXR=%{?_with_soxr:ON}%{?!_with_soxr:OFF} \
     -DWITH_WAYLAND=ON \
     -DWITH_X11=ON \
-    -DWITH_X264=%{?_with_x264:ON}%{?!_with_x264:OFF} \
     -DWITH_XCURSOR=ON \
     -DWITH_XEXT=ON \
     -DWITH_XKBFILE=ON \