upgraded com.google.firebase:firebase-messaging to v17.3.0 in order t…

[PiercarloSlavazza]

upgraded com.google.firebase:firebase-messaging to v17.3.0 in order to fix flutter/flutter#19004 as suggested here firebase/quickstart-android#588 (comment)

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[PiercarloSlavazza]

I signed it!

[googlebot]

CLAs look good, thanks!

[bkonyi]

Thanks!

[bkonyi]

@cbracken, we should publish a new version to pub with this fix.