Upgrade to Sphinx v7

docs/requirements.txt

@@ -1,10 +1,10 @@
-sphinx < 7.3
-sphinx-immaterial == 0.11.11
+sphinx == 7.3.7
+sphinx-immaterial == 0.11.14
 # For some reason, if the below versions aren't specified, the dependency resolution takes 18 minutes in CI.
-myst-parser == 0.18.1
-sphinx-design  == 0.5.0
-sphinx-last-updated-by-git == 0.3.6
+myst-parser == 3.0.1
+sphinx-design  == 0.6.0
+sphinx-last-updated-by-git == 0.3.7
 sphinx-math-dollar == 1.2.1
-ipykernel == 6.26.0
-myst-nb == 0.17.2
+ipykernel == 6.29.5
+myst-nb == 1.1.1
 pickleshare == 0.7.5  # Needed by ipykernel