chore(deps): update sphinx requirement from ==7.* to >=7,<10 (#498)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

setup.cfg

@@ -67,7 +67,7 @@ dev =
     trio-typing[mypy]>=0.6,<0.11
     types-cryptography==3.3.23.2
 docs =
-    sphinx==7.*
+    sphinx>=7,<10
     sphinx-rtd-theme>=2,<4
 
 [options.package_data]