disable natural spawning of bosses in maze

[c86ec23b-fef1-4979-b2fa-b9adc351b8cc]

Why:

Closes [issue link]

Summarize what's being changed (include any screenshots, code, or other media if available):

Confirm the following:

• [x] I have tested these changes (by compiling, running, and playing) and have seen no unintended differences in gameplay

[ABCxFF]

Looks good for now - later on will use "game config" to store this kind of setting