message: Remove `disableMarkdown` setting
  This was used by the old composer to control whether to interpret text as markdown prior to sending.
  The new setting is `MessageComposerInput.isRichTextEnabled`.
diff: @@ -89,10 +89,6 @@ const SETTINGS_LABELS = [
  id: 'hideRedactions',
  label: 'Hide removed messages',
  },
  - {
  - id: 'disableMarkdown',
  - label: 'Disable markdown formatting',
  - },
  {
  id: 'enableSyntaxHighlightLanguageDetection',
  label: 'Enable automatic language detection for syntax highlighting',
  