Revert "Decode path for createElementInDirectoryPath endpoint"

[antoinebhs]

Reverts #156: the issue arises because the path is encoded twice when the request is built in case-import-server (gridsuite/case-import-server#15), not because it's not decoded in directory-server.
This double encoding seems to be repeated in other places in our codebase when building a URI.
The pattern is the following where a first encoding is done in:

        String path = UriComponentsBuilder
                .fromPath([...])
                .queryParam([...])
                .toUriString(); // encoded here

And a second one when using restTemplate.exchange()
There are other places in our code where we decode while we should probably just not encode twice:
https://github.com/gridsuite/loadflow-server/blob/32904c78c88b4fcee92108581acfbab1b9a2d24a/src/main/java/org/gridsuite/loadflow/server/LoadFlowController.java#L85

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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