Lower the chance for unarmed BRDM in GM East enemy preset

[veteran29]

Q	A
Bug fix?	no
New feature?	no
Needs wipe?	no

Description:

Just started a session in GM version and that damn harmless thing was driving around everywhere.

Content:

• [x] Updated GM East enemy preset

Successfully tested on:

• [x] Local MP
• [ ] Dedicated MP