sound: Remove need for translating speaker test button tooltip
Splitting the translation for the CcSpeakerTestButton tooltip is not
ideal. However, fixing that would require keeping track of all the
pa_channel_position_t
and translating all speaker names as well.
From context of the dialog, it's obvious that it is about testing speakers, so we can also go with tooltips like "Front Left" instead of "Front Left Speaker".
We then don't need any translations. Partially reverts commit a8148b40, but keeps the tooltips and screen reader output is the same now as before a8148b40.
Fixes #2905 (closed)