component/alsa: Do not disable pcm, firefox needs it

Without pcm, firefox will crash with this error when playing sound
```
parts/firefox/firefox: relocation error:
/srv/slapgrid/slappart11/srv/runner/software/88ef27d24c6e0a792f72f568146a3838/parts/firefox/libxul.so:
symbol snd_pcm_open, version ALSA_0.9 not defined in file libasound.so.2 with link time reference
```
libasound.so does not contain this symbol if built with --disable-pcm

component/alsa/buildout.cfg

@@ -11,7 +11,6 @@ configure-options =
   --disable-static
   --disable-aload
   --disable-mixer
-  --disable-pcm
   --disable-rawmidi
   --disable-hwdep
   --disable-seq