codec_builtin.c: Adjust some of the quality scores to reflect reality.

codec_builtin.c: Adjust some of the quality scores to reflect reality.

Among the lower-quality voice codecs, some of the quality scores did
not make sense relative to each other.

For instance, quality-wise, G.729 > G.723 > PLC10.
However, current scores do not uphold these relationships.

Tweak the scores slightly to reflect more accurate relationships.

Resolves: #1501