Use DnsPacket.toString() for DnsSvcbPacket

All the important log message, such as SVCB records, can be printed
by DnsPacket.toString(), so there's no need to override toString()
in DnsSvcbPacket.

Bug: 240259333
Test: atest ConnectivityCoverageTests
Change-Id: I8d8f57524ce07d0177a39a9c3f87146d8eb51943
1 file changed