leaudio: Fix for disconnecting ACL

Don't clear conn_id before DisconnectACL is called.
This will be cleared in OnGattDisconnected function.
It would affect handling stream timeout

Bug: 270677410
Tag: #feature
Test: atest BluetoothInstrumentationTests
Change-Id: Ia6a61e8527dfc931f6d16a63e23ac26cb9b40a34