fix(android): suppress R8 warnings for optional push provisioning classes

[1kuko3]

Summary

Add -dontwarn com.stripe.android.pushProvisioning.** to the library's consumer ProGuard rules (android/proguard-rules.txt), next to the existing -dontwarn for TapAndPay.

Motivation

Fixes #1700.

com.stripe:stripe-android-issuing-push-provisioning is a compileOnly dependency. As android/build.gradle notes, apps add it themselves only when they use push provisioning. The SDK's pushprovisioning package still references its classes, so any app that enables R8 without that dependency fails :app:minifyReleaseWithR8:

ERROR: Missing classes detected while running R8. Please add the missing classes or apply additional keep rules that are generated in .../missing_rules.txt.
Missing class com.stripe.android.pushProvisioning.PushProvisioningActivity$g (referenced from: void com.reactnativestripesdk.pushprovisioning.PushProvisioningProxy$createActivityEventListener$listener$1.onActivityResult(...))
Missing class com.stripe.android.pushProvisioning.PushProvisioningActivityStarter$Args (referenced from: void com.reactnativestripesdk.pushprovisioning.DefaultPushProvisioningProxy.beginPushProvisioning(...))

The code is already built for these classes to be missing: PushProvisioningProxy checks for them with Class.forName before use and logs instead of crashing. R8 doesn't know that, so each app currently has to add this rule itself, as the workarounds in #1700 show. This matters more now that the Expo SDK 58 template enables R8 for release builds by default.

Apps that do include push provisioning are unaffected: their classes are present, and the existing -keepclassmembers rule for com.stripe.android.pushProvisioning.** still applies.

Testing

• I tested this manually
• I added automated tests

In our Expo SDK 58 app (React Native 0.88, AGP 9.2.1, Gradle 9.4.1, @stripe/stripe-react-native 0.63.0, push provisioning dependency not installed):

• without the rule, :app:minifyReleaseWithR8 fails with the missing-class errors above;
• with this rule added only to the library's proguard-rules.txt and no app-level rule, :app:minifyReleaseWithR8 passes, and the R8 mapping contains no com.stripe.android.pushProvisioning classes.

Documentation

Select one:

• I have added relevant documentation for my changes.
• This PR does not result in any developer-facing changes.

[cttsai-stripe]

Thank you!