Update macOS launch script for 1.4.5 multiplayer hotfix

[Pathoschild]

Stardew Valley received a hotfix on July 2nd to fix multiplayer on Linux/macOS. We need to update SMAPI's launcher script (in src/SMAPI.Installer/assets/unix-launcher.sh) to match, specifically by setting LC_ALL="C" when launching the game.

To do

• Update launch script for Linux.
• Update launch script for macOS.

[Pathoschild]

Done in develop for the upcoming SMAPI 3.11.0.