fix: correct MDX comment syntax and exclude from prettier (#10556)

Prettier incorrectly escapes JSX comment markers (\`/* */\` → \`\/*
*\/\`) inside these two MDX files' code blocks, breaking the comment
syntax. Excludes both files from prettier and fixes the existing bad
escaping.

Split out of the Node 24 branch (#10555), where it was an unrelated
change picked up along the way.

Author: GiladShoham

.prettierignore

@@ -1,3 +1,6 @@
 fixtures
 e2e/fixtures
-components/legacy/e2e-helper/excluded-fixtures
+components/legacy/e2e-helper/excluded-fixtures
+# MDX files with JSX comments that prettier incorrectly escapes
+scopes/react/aspect-docs/react/react.mdx
+scopes/react/ui/loader-fallback/loader-fallback.docs.mdx