sysutils/navi: update to 2.15.0

Breaking changes:
-Make --map behave as function body (#468)

New features:
-Make preview var content streamable
-Improve bash and zsh widgets (#486)

Fixes:
-If command not found in cheatsh, report and return
-Make preview window show mapped values

Code quality:
-Fix warnings (#464)
-Fix all new warnings (#467)
-Move common helpers to src/ (#465)
-Bump all dependencies (#466)
-Remove unused code for global flag
-Correctly show preview var window for --multi (#472)
-Refactor finder packages (#473)
-Refactor terminal_width package
-Refactor core package (#476)
-Refactor fetcher packages (#477)
-Rename display package
-Add instructions for shell widget customization (#480)
-Use Pathbufs appropriately (#481)
-Use remove_dir_all crate (#482)
-Use crossterm instead of termion and terminal_width
-Refactor env_vars package (#485)

(pin)