Remove mod_celt and mod_vp8 remnants

Jeff added these directories back in commit 345e50d which causes our
debian/bootstrap.sh to add these back to debian/control-modules.

debian/control-modules

@@ -299,10 +299,6 @@ Description: mod_bv
  Adds mod_bv.
 Build-Depends: libbroadvoice-dev
 
-Module: codecs/mod_celt
-Description: Adds mod_celt
- Adds mod_celt.
-
 Module: codecs/mod_codec2
 Description: mod_codec2
  Adds mod_codec2.
@@ -375,10 +371,6 @@ Module: codecs/mod_theora
 Description: mod_theora
  Adds mod_theora.
 
-Module: codecs/mod_vp8
-Description: Adds mod_vp8
- Adds mod_vp8.
-
 Module: codecs/mod_vpx
 Description: VP8/VP9 video codec
  This module adds the VP8 video codec, also known as WebM.