Update gsi_enkf.sh hash to 457510c (#2514)

The `gsi_enkf.fd` hash is updated to bring in revisions to GSI source
code file `src/gsi/correlated_obsmod.F90`. The order in which set up
checks are performed have been modified to allow `gsi.x` to successfully
run retrospective GFS v17 cases with correlated error active.

Resolves #2507