Get rid of CancelOpen from bta_dm_disc_result

Looks like it was added accidentally in aosp/2584253
Please see aosp/2584253/comment/5f10a7c2_8abb90bd/

Bug: 330675788
Bug: 335732980
Flag: com.android.bluetooth.flags.separate_service_and_device_discovery
Test: mma -j32
Change-Id: I6592276d4f9c204897b31cd2afae75d4fbe1f6a5