Update dependency katex to v0.16.20

Author: renovate[bot]

package.json

@@ -26,7 +26,7 @@
     "firebase": "11.1.0",
     "gitalk": "1.8.0",
     "hexo-generator-searchdb": "1.4.1",
-    "katex": "0.16.9",
+    "katex": "0.16.20",
     "lozad": "1.16.0",
     "mathjax": "3.2.2",
     "medium-zoom": "1.1.0",