File validation check is too narrow for log file path validation

[Zodiac1978]

validate_file(...) === 1 only checks one invalid case - Safer check would reject all non-zero invalid codes.
https://github.com/pluginkollektiv/antispam-bee/blob/master/antispam_bee.php#L2376

See also: https://developer.wordpress.org/reference/functions/validate_file/