Correct mmsproxies extra zeros in Greece and Austria

Correct validation errors from APN validator in aosp/2291617

Test: adb shell content query --uri content://telephony/carriers --where numeric='20201'
Test: adb shell content query --uri content://telephony/carriers --where numeric='23207'
Bug: 319190674
Change-Id: Ic1a81bafebac34ee953b06eb714a6cc2e38b1159