Custom-Commands-Compendium should update due to api break change

**Describe the bug**
RefName doesn't exist anymore. But the Custom-Commands-Compendium style refer the old name.
Changes in this commit: https://github.com/jesseduffield/lazygit/commit/6afcc5bda8bbe9d9976fd50740564fe201c3ea41

When running custom commands, we will get this error:
```
template: template:1:50: executing "template" at <.SelectedRemote.RefName>: can't evaluate field RefName in type *custom_commands.Remote
```

**To Reproduce**
no need.

**Expected behavior**
Fix the Doc.

**Screenshots**
no need.

**Version info:**
no need.

**Additional context**
no need.