Update dependency mkdocs-material to v9.1.19 (#156)

Author: slack-oss-bot

.github/workflows/mkdocs-requirements.txt

@@ -7,7 +7,7 @@ Markdown==3.4.3
 MarkupSafe==2.1.3
 mkdocs==1.4.3
 mkdocs-macros-plugin==1.0.2
-mkdocs-material==9.1.18
+mkdocs-material==9.1.19
 mkdocs-material-extensions==1.1.1
 Pygments==2.15.1
 pymdown-extensions==10.0.1