platform-openh264: Don't provide for arm, ppc

The binary from cisco is either x86_64 or i*86, so no need to build for
arm or ppc.
10 jobs for coldtom/publish-openh264-master in 80 minutes and 17 seconds (queued for 1 second)
Status Job ID Name Coverage
  Flatpak
passed #295312770
aarch64
app_aarch64

01:17:45

passed #295312771
armhf
app_arm

00:32:15

passed #295312769
cache_i686 x86_64
app_i686

00:33:19

passed #295312772
ppc64le allowed to fail
app_powerpc64le

00:58:06

passed #295312768
cache_x86_64 x86_64
app_x86_64

00:34:44

 
  Vm
manual #295312775
aarch64 allowed to fail manual
minimal_systemd_vm_aarch64
passed #295312776
armhf
minimal_systemd_vm_arm

00:02:30

passed #295312774
cache_i686 x86_64
minimal_systemd_vm_i686

00:01:12

manual #295312777
ppc64le allowed to fail manual
minimal_systemd_vm_powerpc64le
passed #295312773
cache_x86_64 x86_64
minimal_systemd_vm_x86_64

00:01:14