shorten rolling increment to 32

[garyschulte]

PR description

simple change to state rolling increment for debug_setHead. This PR shortens this interval to 32.

Fixed Issue(s)

Discovered while verifying #7804, chain and state rolling with an interval of 512 can lead to out-of-memory.

confirmed by rolling state 209k blocks back on main to the block referenced in #7804. trace for the block in question attached

trace_block_21030627.json

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[macfarla]

changelog?