Update sphinx requirement from ~=8.0.2 to ~=8.1.3 (#138)

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Author: dependabot[bot]

requirements.txt

@@ -21,7 +21,7 @@ requests~=2.32.3
 six~=1.16.0
 snowballstemmer~=2.2.0
 soupsieve~=2.6
-Sphinx~=8.0.2
+Sphinx~=8.1.3
 sphinx-material~=0.0.36
 sphinxcontrib-applehelp~=2.0.0
 sphinxcontrib-devhelp~=2.0.0