Do not retreat to repair towards stuff outside scroll limits

[KJeff01]

Describe the bug
On Gamma 6 it is possible for units to retreat to repair towards repair facilities before the map allows the scroll limits to include the northern sections again. This will mean assured death in the event you are not quick enough to redirect units away from their path. While this will have to be dealt with before having a repair near the starting point of Gamma 6 after the scroll limits update, they shouldn't seek repairs that are not within the scroll limits to begin with anyway.

To Reproduce
Steps to reproduce the behavior:

1. Enter a mission (very start of Gamma 6) or mod that may have units/structures that can repair outside the scroll limits.
2. Watch units attempt to seek these repairs as valid places to go.

Expected behavior
Repairs should only be counted within the scroll limit bounds.

Your System:

• OS: Any
• Game version: ancient bug

Additional context
Noted during discussions about #3769.