Bump nbconvert from 7.3.0 to 7.3.1 (#485)

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

Author: dependabot[bot]

pyproject.toml

@@ -72,7 +72,7 @@ doc = [
     "jupyter_sphinx==0.4.0",
     "jupytext==1.14.5",
     "myst-parser==1.0.0",
-    "nbconvert==7.3.0",
+    "nbconvert==7.3.1",
     "nbsphinx==0.9.1",
     "notebook==6.5.4",
     "numpydoc==1.5.0",