fix(ui): Upstream security vulnerability markdown-it-katex (#120)

This package was never used, but remained in dependencies, causing security alert.

Author: hawkeye64

ui/package.json

@@ -49,7 +49,6 @@
     "markdown-it-footnote": "^3.0.2",
     "markdown-it-imsize": "^2.0.1",
     "markdown-it-ins": "^3.0.0",
-    "markdown-it-katex": "^2.0.3",
     "markdown-it-mark": "^3.0.0",
     "markdown-it-sub": "^1.0.0",
     "markdown-it-sup": "^1.0.0",