Fix #8462: Don't check whether to grow a town road on water #8471
Motivation / Problem
I'm not a town growth expert, but I don't think towns are supposed to be clearing water tiles to expand on them.
I think the problem is solved by using DC_NO_WATER flag on this situation.
I have no great knowledge of town growth code, but with some tests, towns grow differently with the fix in, when they're near river tiles. But I'm not really sure of the whole impact of this change.
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.
LordAro, CMD_BUILD_ROAD also ends up running CMD_LANDSCAPE_CLEAR and inherits the DC flags from the source.