Fix #12268: Capitalize "Wait to unbunch" order string

[2TallTyler]

Motivation / Problem

We capitalize the first letter of sentence fragments in the order text, like (Stop), (Full load), (Refit to {STRING}), etc.

In #11945 I failed to capitalize the first letter of (wait to unbunch) to be consistent with this pattern.

Description

Capitalize the (Wait to unbunch) order modifier.

Closes #12268.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, game_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker