feat: roof_palette instead of acidia_residential_roof_palette for urban_7_5 and urban_7_6

[0Monet]

Purpose of change (The Why)

roof_palette is a better choice than acidia_residential_roof_palette for these two mapgen.

Describe the solution (The How)

Use roof_palette and its symbols for urban_7_5 and urban_7_6
Merge the two mapgen.

Describe alternatives you've considered

none

Testing

No errors when starting a new game.

Additional context

Screenshots:

Before:

After:

Checklist

Mandatory

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax like closes #1234 in Summary of the PR so it can be closed automatically.
• I've committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.
• I understand that, unless specified otherwise, my contributions will fall under the AGPL v3.0 and/or CC-BY-SA 4.0 licenses