chore: rely on pyproject.toml when building docs

Author: dimaqq

docs/requirements.txt

@@ -21,7 +21,10 @@ passenv =
 
 [testenv:docs]
 deps =
-    -r docs/requirements.txt
+    .[dev]
+    sphinx==5.3.0
+    sphinxcontrib-asyncio
+    sphinx_rtd_theme
 
 allowlist_externals = rm
 commands =