tests/meminfo: Update for addition of "max free sz" output.

tests/micropython/meminfo.py.exp

 mem: total=\\d\+, current=\\d\+, peak=\\d\+
 stack: \\d\+ out of \\d\+
 GC: total: \\d\+, used: \\d\+, free: \\d\+
- No. of 1-blocks: \\d\+, 2-blocks: \\d\+, max blk sz: \\d\+
+ No. of 1-blocks: \\d\+, 2-blocks: \\d\+, max blk sz: \\d\+, max free sz: \\d\+
 mem: total=\\d\+, current=\\d\+, peak=\\d\+
 stack: \\d\+ out of \\d\+
 GC: total: \\d\+, used: \\d\+, free: \\d\+
- No. of 1-blocks: \\d\+, 2-blocks: \\d\+, max blk sz: \\d\+
+ No. of 1-blocks: \\d\+, 2-blocks: \\d\+, max blk sz: \\d\+, max free sz: \\d\+
 GC memory layout; from \[0-9a-f\]\+:
 ########
 qstr pool: n_pool=1, n_qstr=\\d, n_str_data_bytes=\\d\+, n_total_bytes=\\d\+