security/vuxml: Mark security/zeek < 8.0.8 as vulnerable as per:

https://github.com/zeek/zeek/releases/tag/v8.0.8

This release fixes the following potential DoS vulnerability:

• A specially-crafted series of MIME headers sent via SMTP or HTTP could cause Zeek to use large amounts of memory and potentially crash.

Reported by: Tim Wojtulewicz