shells/oh-my-posh: update to 16.0.0

Bug Fixes
- cache: only store template cache on primary and transient (b51d1de)

Features
- font: update to Nerd Font V3 (9663a29)

BREAKING CHANGES
- font: this deprecates support for Nerd Font V2 and requires a compatible
  V3 Nerd Font. Note for users experiencing issues with icons, update to the
  latest Nerd Font of your choice

(pin)