ci: drop stale dependencies

ffmpeg, epoll-shim, libpng were dependencies for client examples.
These have been split into a separate repository so we no longer
need to install them.

.builds/alpine.yml

@@ -1,7 +1,6 @@
 image: alpine/edge
 packages:
   - eudev-dev
-  - ffmpeg-dev
   - glslang
   - libdisplay-info-dev
   - libinput-dev

.builds/archlinux.yml

@@ -1,7 +1,6 @@
 image: archlinux
 packages:
   - clang
-  - ffmpeg
   - libinput
   - libdisplay-info
   - libliftoff

.builds/freebsd.yml

@@ -1,7 +1,6 @@
 image: freebsd/latest
 packages:
   - devel/evdev-proto
-  - devel/libepoll-shim
   - devel/libudev-devd
   - devel/meson # implies ninja
   - devel/pkgconf
@@ -9,13 +8,10 @@ packages:
   - graphics/libdrm
   - graphics/libliftoff
   - graphics/mesa-libs
-  - graphics/png
   - graphics/vulkan-headers
   - graphics/vulkan-loader
   - graphics/wayland
   - graphics/wayland-protocols
-  - multimedia/ffmpeg
-  - x11/libX11
   - x11/libinput
   - x11/libxcb
   - x11/libxkbcommon