Bump doc requirements.

docs/requirements.txt

@@ -6,19 +6,19 @@
 #
 alabaster==0.7.12
     # via sphinx
-attrs==21.2.0
+attrs==21.4.0
     # via jsonschema
 babel==2.9.1
     # via sphinx
 beautifulsoup4==4.10.0
     # via furo
 certifi==2021.10.8
     # via requests
-charset-normalizer==2.0.9
+charset-normalizer==2.0.10
     # via requests
 docutils==0.17.1
     # via sphinx
-furo==2021.11.23
+furo==2022.1.2
     # via -r docs/requirements.in
 idna==3.3
     # via requests
@@ -28,15 +28,15 @@ jinja2==3.0.3
     # via sphinx
 file:.#egg=jsonschema
     # via -r docs/requirements.in
-lxml==4.6.5
+lxml==4.7.1
     # via -r docs/requirements.in
 markupsafe==2.0.1
     # via jinja2
 packaging==21.3
     # via sphinx
 pyenchant==3.2.2
     # via sphinxcontrib-spelling
-pygments==2.10.0
+pygments==2.11.2
     # via
     #   furo
     #   sphinx
@@ -46,13 +46,13 @@ pyrsistent==0.18.0
     # via jsonschema
 pytz==2021.3
     # via babel
-requests==2.26.0
+requests==2.27.1
     # via sphinx
 snowballstemmer==2.2.0
     # via sphinx
 soupsieve==2.3.1
     # via beautifulsoup4
-sphinx==4.3.1
+sphinx==4.3.2
     # via
     #   -r docs/requirements.in
     #   furo
@@ -69,7 +69,7 @@ sphinxcontrib-qthelp==1.0.3
     # via sphinx
 sphinxcontrib-serializinghtml==1.1.5
     # via sphinx
-sphinxcontrib-spelling==7.3.0
+sphinxcontrib-spelling==7.3.2
     # via -r docs/requirements.in
 urllib3==1.26.7
     # via requests