[CDM] Remove mac address while storing last removed association.

Sample dump:
1740519388424 shell Association{mId=5, mUserId=0, mPackageName='testapp', mDeviceMacAddress=null, mDisplayName='', mDeviceProfile='null', mSelfManaged=false, mAssociatedDevice=null, mNotifyOnDeviceNearby=false, mRevoked=false, mPending=false, mTimeApprovedMs=Tue Feb 25 13:36:20 PST 2025, mLastTimeConnectedMs=None, mSystemDataSyncFlags=0, mDeviceId='null}

Fix: 397461312
Flag: EXEMPT bugfix
Test: manual
Change-Id: I1ecd8ad8d6579191197fae36a25048e034e725a7