Updated sphinx to v5 in docs requirements - this has already been done in the conversion branch but I want it in master

Author: DavidT3

docs/requirements.txt

@@ -11,7 +11,7 @@ scipy>=1.4.1
 pyabel>=0.8.3
 corner>=2.1.0
 emcee>=3.0.2
-Sphinx~=3.1.2
+Sphinx~=5.0
 nbsphinx
 sphinx_rtd_theme>=0.3.1
 ipython
@@ -23,4 +23,4 @@ docutils==0.17
 ipympl>=0.9.1
 exceptiongroup~=1.1.0
 urllib3<2.0.0
-jinja2<3.1
+jinja2<3.1