Conflicting Keybinding when using Fish Shell

## Prerequisites
- [x] I have searched open and closed issues for duplicates.

## Describe the bug
The `alt+Up` keybinding introduced in 5.3.3 conflict with the alt+up keybinding of fish (used to scroll through previous arguments. Maybe allowing the rebinding of keybindings could help.

### To Reproduce
Steps to reproduce the behavior:
1. Install Fish
2. Press alt+Up

## Platform Information
If you can't please share:
- OS: elementary OS
- OS Version: Juno
- Hardware info

Please check what applies:
- [x] I'm using the latest released stable version