Fix RTD configuration

[t-reents]

No description provided.

[Copilot]

Pull request overview

This PR modernizes the ReadTheDocs (RTD) configuration by migrating from a separate requirements file to using pyproject.toml's optional dependencies feature. The sphinx dependency is now properly declared in the project metadata, and the RTD configuration is updated to use the new dependency installation method.

Changes:

• Migrated documentation dependencies from docs/requirements_for_rtd.txt to pyproject.toml optional dependencies
• Updated .readthedocs.yml to use extra_requirements instead of a separate requirements file
• Added sphinx version constraint to the new docs optional dependency group

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
pyproject.toml	Added docs optional dependency group with sphinx constraint
docs/requirements_for_rtd.txt	Removed file (previously contained only setuptools requirement)
.readthedocs.yml	Updated to use extra_requirements for docs instead of separate requirements file

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[Copilot]

The version constraint "sphinx<7.2" appears overly restrictive. Consider using a more standard constraint like "sphinx>=4.0" or "sphinx>=4.0,<9.0" to allow for newer versions while maintaining compatibility. The current constraint would prevent using Sphinx 7.2 or later, which may include important bug fixes and features.

Suggested change

	"sphinx<7.2",
	"sphinx>=4.0,<9.0",