Use API 30 for instrumentation tests

[seadowg]

We should be using our target API with Firebase, so we catch problems on the newest (and often strictest) OS.

Notes

I did a quick recce on this and found there are a bunch of failures (in the 20s) after moving to an API 30 device. It looks like they are all related to these problems:

• [x] Toast assertions don't work (https://github.com/android/android-test/issues/803)
• [x] Middle toasts show as dialogs and need to be closed before moving on (FormValidationTest)
• [x] Not permitted to create temp files (IntentGroupTest)
• [x] UIAutomator notification assertions are potentially flakey?

[seadowg]

This should hopefully be easier with Espresso 3.5.0 as it seems like there's a probable fix for https://github.com/android/android-test/issues/444 in there. We should block this issue on a stable release of 3.5.0 (release log here)