refactor: remove markdown-it-plantuml dep

package.json

@@ -100,7 +100,6 @@
     "markdown-it-imsize": "2.0.1",
     "markdown-it-mark": "3.0.0",
     "markdown-it-mathjax": "2.0.0",
-    "markdown-it-plantuml": "1.4.1",
     "markdown-it-sub": "1.0.0",
     "markdown-it-sup": "1.0.0",
     "markdown-it-task-lists": "2.1.1",