Fix keyword detection regression in Mic.passiveListen()

This is a one-line bugfix PR.

Prior to commit 6bb87e20423e41f1bb79e6af285fe4d49cf1359a (Handle all Google Speech options, Pull Request #148), passive listen checked if the transcribed phrase contained the keyword. Since then, it only detects if the transcribed phrase was *exactly* the keyword. When using Pocketsphinx, it often happens that additional words are transcribed (like `JASPER OF`), so that saying the keyword sometimes did not result in an active listen call. With this commmit, this regression will be fixed and the old behaviour is restored.