Update Android CI to run VM with SDK version 32

[ikurek]

Currently, the CI runner for Android uses SDK version 21 and 29. To make sure Ably is compatible with latest versions of Android, we can replace the SDK 29 emulator with the latest Android SDK available (32). We can also consider changing the runner construction to execute sequentially, since running them in parallel seems to cause conflicts and CI failures (see #232)

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