Fix line continuation check in config parser

Fix line continuation check in config parser

Fixes #8038: Previously, line continuation logic did not account for the 'again' flag, which could cause incorrect removal of a backslash character in the middle of a line. This fix ensures that line continuation is correctly handled only when 'again' is false, thus improving the reliability of the configuration parser.

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24890)