Revert addition of a11y stream in VolumeDialogController

Revert addition of STREAM_ACCESSIBILITY as R.array.volume_stream_titles
  needs to contain STREAMS.length entries in all languages,
  whereas this had only been done for the default system language.

Test: boot in a different language than en-US
Bug: 33260083
Change-Id: If869c5f913bb42b94eeb3fa2e1b6f575a6f7ca70