Update security/bro to 2.5.2

[leres]

Summary

Proposed commit message:

Update to 2.5.2. Changes since 2.5.1:

 - Patch OOB write in content-line analyzer:

     https://bro-tracker.atlassian.net/browse/BIT-1856

     A combination of packets can trigger an out of bound write of
     '0' byte in the content-line analyzer.

Reviewed by: ? (mentor)
Approved by: ? (mentor)
Differential Revision: ?

[ler]

LGTM