Bump public-transport-enabler to restore DB support

[InsanePrawn]

Hi, kinda just throwing this out there: I bumped the minsdk and pte lib and added the minimum required changes until the DB api started working on my phone again.
I'm not an android dev and have no idea what that gradle witness file is.
Build locally using ./gradlew build

I also didn't mess around with desugaring as hinted at in #979 (comment)

Might be of interest for people who want to build a working version until 2.2.4 is published :)

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[cla-bot]

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[InsanePrawn]

I accept the agreement