Remove obsolete advice about doubling backslashes in regex escapes.
Remove obsolete advice about doubling backslashes in regex escapes.

Standard-conforming literals have been the default for long enough that
it no longer seems necessary to go out of our way to tell people to write
regex escapes illegibly.

zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl