Pin a working jinja2 version

TimWolla · TimWolla · commit 2494c815367b · 2022-04-22T15:37:41.000+02:00
see https://twitter.com/readthedocs/status/1507388916013314048
diff --git a/requirements.txt b/requirements.txt
@@ -4,3 +4,4 @@ mkdocs-git-revision-date-plugin==0.3.1
 mkdocs-macros-plugin==0.6.0 
 mkdocs-material==7.3.4
 mkdocs==1.2.3
+jinja2<3.1.0
