[BUG] docs: invalid escaping for custom command argument example

Question

## Bug Description
(very minor) mistake in the docs: https://docs.anthropic.com/en/docs/claude-code/slash-commands#arguments

```bash
# Command definition
echo "Fix issue #$ARGUMENTS following our coding standards" > .claude/commands/fix-issue.md

# Usage
> /project:fix-issue 123
```

But that obviously wouldn't work:

```console
bash$ echo "Fix issue #$ARGUMENTS following our coding standards"
Fix issue # following our coding standards
```

## Expected Docs
```
# Command definition
echo 'Fix is