Remove minifyEnabled flag for Android for a readable Crashlytics stack trace

[nilsreichardt]

We had the problem that our stack trace was not readable (see #835). This is a huge problem for us because we want to detect errors in our beta and alpha versions and fix them. Without the stack trace it's super hard to fix them.

I'm pretty sure that the minifyEnabled flag obfuscates the stack trace. I would value the stack trace much higher than a bit smaller APK file. But I also made the test:

1. Run sz build android --output-type apk (with minifyEnabled): 54.0 MB
2. Run fvm flutter clean && sz build android --output-type apk (without minifyEnabled): 54.0 MB

Fixes #835

[github-actions]

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