Refactor-v-html-markdown.vue

What does this MR do and why?

Replaces dangerous v-html with our safe directive v-safe-html
Closes - #241888 (closed) Remove v-html from app/assets/javascripts/notebook/cells/markdown.vue

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app/assets/javascripts/notebook/cells/markdown.vue

 <script>
 import katex from 'katex';
 import marked from 'marked';
+import { GlSafeHtmlDirective as SafeHtml } from '@gitlab/ui';
 import { sanitize } from '~/lib/dompurify';
 import { hasContent, markdownConfig } from '~/lib/utils/text_utility';
 import Prompt from './prompt.vue';
@@ -138,6 +139,9 @@ export default {
   components: {
     prompt: Prompt,
   },
+  directives: {
+    SafeHtml,
+  },
   inject: ['relativeRawPath'],
   props: {
     cell: {
@@ -159,7 +163,7 @@ export default {
 <template>
   <div class="cell text-cell">
     <prompt />
-    <div class="markdown" v-html="markdown /* eslint-disable-line vue/no-v-html */"></div>
+    <div v-safe-html="markdown" class="markdown"></div>
   </div>
 </template>