Monorepo support warning on Getting Started page no longer required

## Documentation Error

### Description

The warning regarding the lack of monorepo support on the [Getting Started](https://github.com/python-semantic-release/python-semantic-release/blob/f77c5984c20779a51d4105b75edd152ce377b1a5/docs/concepts/getting_started.rst?plain=1#L178) page is no longer required as of v10.4.0.

