Bump doc requirements.

Author: Julian

docs/requirements.txt

@@ -20,11 +20,11 @@ contourpy==1.0.7
     # via matplotlib
 cycler==0.11.0
     # via matplotlib
-docutils==0.19
+docutils==0.20.1
     # via sphinx
 fonttools==4.39.4
     # via matplotlib
-furo==2023.3.27
+furo==2023.5.20
     # via -r docs/requirements.in
 idna==3.4
     # via requests
@@ -63,9 +63,9 @@ pyparsing==3.0.9
     # via matplotlib
 python-dateutil==2.8.2
     # via matplotlib
-referencing==0.28.1
+referencing==0.28.5
     # via jsonschema-specifications
-requests==2.30.0
+requests==2.31.0
     # via sphinx
 rpds-py==0.7.1
     # via referencing
@@ -75,7 +75,7 @@ snowballstemmer==2.2.0
     # via sphinx
 soupsieve==2.4.1
     # via beautifulsoup4
-sphinx==6.2.1
+sphinx==7.0.1
     # via
     #   -r docs/requirements.in
     #   furo