Fix readthedocs build

Author: RazerM

.readthedocs.yml

@@ -8,10 +8,13 @@ formats:
 build:
   os: ubuntu-22.04
   tools:
-    python: "3"
+    python: "3.13"
 
 python:
   install:
     - requirements: ci/rtd-requirements.txt
     - method: pip
       path: .
+
+sphinx:
+  configuration: docs/source/conf.py

ci/rtd-requirements.txt

@@ -1,4 +1,4 @@
 # RTD is currently installing 1.5.3, which has a bug in :lineno-match:
-sphinx >= 4.0, < 6.2
+sphinx >= 6.0
 sphinx_rtd_theme
 sphinxcontrib-trio