Disabling 4 VIET-specific decision files from VIso4

The following decision files are now additionally blank:

VIET_heresy_decisions.txt, VIET_misc_decisions.txt,
VIET_misc_religion_decisions.txt, VIET_West_Africa_decisions.txt

This should leave the following ones active:

VIET_Pagan_decisions, VIET_Z_Customization_Options,
realm_decisions, succession_laws