fix: remove config_path in Config (#431)

## Description

Fix as a pre-requisite to ecmwf/anemoi-utils#223
because
the class hiearchy will change and the removed line created an
exception.

## What problem does this change solve?
<!-- Describe if it's a bugfix, new feature, doc update, or breaking
change -->

## What issue or task does this change relate to?
<!-- link to Issue Number -->

##  Additional notes ##
<!-- Include any additional information, caveats, or considerations that
the reviewer should be aware of. -->

***As a contributor to the Anemoi framework, please ensure that your
changes include unit tests, updates to any affected dependencies and
documentation, and have been tested in a parallel setting (i.e., with
multiple GPUs). As a reviewer, you are also responsible for verifying
these aspects and requesting changes if they are not adequately
addressed. For guidelines about those please refer to
https://anemoi.readthedocs.io/en/latest/***

By opening this pull request, I affirm that all authors agree to the
[Contributor License
Agreement.](https://github.com/ecmwf/codex/blob/main/Legal/contributor_license_agreement.md)

Author: b8raoult

src/anemoi/datasets/create/config.py

@@ -132,7 +132,6 @@ def __init__(self, config: str | dict | None = None, **kwargs):
             Additional keyword arguments to update the configuration.
         """
         if isinstance(config, str):
-            self.config_path = os.path.realpath(config)
             config = load_any_dict_format(config)
         else:
             config = deepcopy(config if config is not None else {})