suricata: Update to 6.0.15

suricata: Update to 6.0.15

Excerpt from changelog:

"6.0.15 -- 2023-10-18

Security #6363: mime: quadratic complexity in MimeDecAddEntity (6.0.x backport)
Bug #6407: email: disabled fields in suricata.yaml also get logged (6.0.x backport)
Bug #6403: detect: multi-level tunneling inspection fails (6.0.x backport)
Bug #6377: byte_jump with negative post_offset before start of buffer failure (6.0.x backport)
Task #6364: decode: add drop reason for stream reassembly memcap (6.0.x backport)"

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Reviewed-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>