Fix deselecting calendar days on contribution graph

What does this MR do?

Fix deselecting calendar days on contribution graph

Are there points in the code the reviewer needs to double check?

Shouldn't be

Why was this MR needed?

In master, you can currently deselect a calendar day after selecting but you cannot reselect that day.

Screenshots (if relevant)

Before:

After:

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #22381 (closed)