Bump mkdocs-material from 7.1.8 to 8.1.3 (#1154)

dependabot[bot] · web-flow · commit 3bf637222ab1 · 2021-12-21T16:47:19.000+01:00
diff --git a/requirements/requirements_doc.txt b/requirements/requirements_doc.txt
@@ -1,2 +1,2 @@
 mkdocs==1.1.2
-mkdocs-material==7.1.8
+mkdocs-material==8.1.3
