Fix RTL displaCy dependency labels

[lxingy3]

Description

Fixes #4854.

This updates the displaCy dependency renderer so dependency labels no longer depend on the SVG side attribute. Browser support for side is inconsistent, which makes RTL dependency labels appear reversed or upside down in Chrome and Safari.

The visible dependency arc is unchanged. The label now follows a separate invisible path, and RTL rendering reverses that label path so the text direction stays readable without relying on side.

Types of change

Bug fix.

Testing

• python -m py_compile spacy\displacy\render.py spacy\displacy\templates.py spacy\tests\test_displacy.py
• git diff --check
• Focused pytest was not run because the local Python environment does not have spaCy's runtime dependencies installed (thinc is missing before test collection).

Checklist

• I confirm that I have the right to submit this contribution under the project's MIT license.
• I ran the tests, and all new and existing tests passed.
• My changes don't require a change to the documentation, or if they do, I've added all required information.