Add docs link for confidential and locked issues

What does this MR do?

Adds documentation links for locked and confidential issues to note compose forms.

Locked issue

Before	After

Confidential issue

Before	After

Confidential and Locked issue

Before	After

Locked discussions widget

Before	After

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Closes #37495 (closed)