Fix documentation for pg_stat_statements JIT deform_counter

Hi,

I was adding support for the new pg_stat_statements JIT deform_counter in PoWA
when I realized that those were added after jit_generation_time in the
documentation while they're actually at the end of the view. I'm adding Daniel
in Cc as the committer of the original patch.

It looks like there was some will to put them earlier in the view too, but
since it would require some additional tests in the SRF they probably just
ended up at the end of the view while still being earlier in the struct.
Anyway, it's not a big problem but all other fields are documented in the
correct position so let's be consistent.

Trivial patch attached.