CLI11: simplify CLI11.wrap

We no longer need a `[provide]` statement and it ends up causing a
meson warning:

```
WARNING: Variable 'CLI11_dep' in the subproject 'subprojects/CLI11' is not found
```

This is no longer needed because CLI11 has an explicit dependency
override statement in the project meson.build.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ib29cfea743206e3244f91ac2e5f6806222ece462