Update discussion.position when saving note

What does this MR do?

For: #228907 (closed)

Fixes mouse over highlighting not updating after saving a note. See video below.

Screenshots

It works!

Screen_Recording_2020-07-31_at_2.37.24_PM

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