Getting Rid of Annoying Buzzing Sound from Multimeter
Page 21 of the user manual states:

WRONG CONNECTION INDICATION
The [buzzer] icon will appear in the upper right corner of the display
and the buzzer will sound whenever the positive test lead is
inserted into the 20A or uA/mA input jack and a non-current
function is selected. If this occurs, turn the meter off and reinsert the test lead into the proper input jack for the function selected.

You can disconnect it or just avoid having the leads in the wrong socket.