Don't dump pending_discovery

`pending_discovery` is non-empty only while service
discovery is ongoing.
During this time, a new service could be added,
leading to a race condition.

To prevent this potential concurrency issue,
`pending_discovery` is no longer dumped.

Bug: 372121030
Flag: EXEMPT, log only change
Test: atest BluetoothInstrumentationTests
Change-Id: Id23430a3b0d86b1adc81437b222a7e3f336462be