Remove rich_content_editor v-model

What does this MR do?

Improves the separation of concerns between parseSourceFile, it's use in edit_area.vue, and rich_content_editor's initialValue resetting.

Screenshots

n/a

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Closes #220987 (closed)