builtin.conf: remove unneeded vlang/alang/slang lines

ac725764ec originally added these to
prevent those profiles from having auto as a value. However the auto
value was removed in 53d032374d later. So
having these lines here no longer serves any purpose since the default
value for slang is NULL once again (vlang/alang were never needed here).

etc/builtin.conf

@@ -28,9 +28,6 @@ input-default-bindings=no
 input-vo-keyboard=no
 # OSX/Cocoa global input hooks
 input-media-keys=no
-vlang=
-alang=
-slang=
 
 [encoding]
 vo=lavc
@@ -42,9 +39,6 @@ resume-playback=no
 load-scripts=no
 osc=no
 framedrop=no
-vlang=
-alang=
-slang=
 
 [fast]
 scale=bilinear