Remove supporting pawns

Tested in no-regression mode

Passed both STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 44957 W: 7984 L: 7903 D: 29070

and LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 12396 W: 1916 L: 1783 D: 8697

Bench: 7907885
Increment pv_instability immediately even in the middle of an iteration.
Remove depth=50 restriction on pv_instability.
bench: 6921356
Increment pv_instability immediately even in the middle of an iteration.
Remove depth=50 restriction on pv_instability.
6921356
Increment pv_instability immediately even in the middle of an iteration.
Remove depth=50 restriction on pv_instability. Take 2
6921356
Increment pv_instability immediately even in the middle of an iteration.
Remove depth=50 restriction on pv_instability.  Tkae 3
6921356