YJIT: increase max chain depth for expandarray

[maximecb]

Expand the chain depth from 2 to 4 since this gets tripped some percentage of the time on SFR:

expandarray exit reasons: 
       chain_max_depth:  1,345,017 (85.0%)
                 splat:    181,665 (11.5%)
             not_array:     54,494 ( 3.4%)
    comptime_not_array:        507 ( 0.0%)

...

Top-20 most frequent exit ops (100.0% of exits):
                    checkmatch:  8,593,546 (36.0%)
                   invokesuper:  4,080,558 (17.1%)
                 setlocal_WC_0:  3,828,583 (16.1%)
            getblockparamproxy:  1,778,545 ( 7.5%)
                   expandarray:  1,581,683 ( 6.6%)
        opt_send_without_block:  1,366,974 ( 5.7%)
          opt_getconstant_path:  1,328,064 ( 5.6%)
                 opt_aset_with:    362,129 ( 1.5%)
                      opt_aref:    352,641 ( 1.5%)

[noahgibbs]

Makes sense. LGTM.