Fix deprecated macOS dependency syntax in deeper cask

Homebrew is now warning that the [`deeper`](https://github.com/f/deeper) cask in this tap uses the deprecated string comparison form for `depends_on macos:`.

Warning:

```text
Warning: Calling string comparison format for `depends_on macos:` is deprecated! Use `depends_on macos: :tahoe` instead.
Please report this issue to the f/homebrew-tap tap (not Homebrew/* repositories), or even better, submit a PR to fix it:
/opt/homebrew/Library/Taps/f/homebrew-tap/Casks/deeper.rb:10
```

Current line on `main`:

```ruby
depends_on macos: ">= :tahoe"
```

Suggested change:

```ruby
depends_on macos: :tahoe
```

Open Casks/deeper.rb and inspect the depends_on macos: declaration at line 10. Replace the deprecated string comparison form with the suggested symbol form, then verify that the cask no longer triggers the reported Homebrew warning.

Written by the indexing model from the issue text.