Use /react as the primary command for adding emoji reaction

What does this MR do and why?

/react was added as an alias for /award quick action.

This MR makes /react the primary command name and /award an alias. The documentation update was already done in !138892 (merged) because I mistakenly thought I was making /react the primary command in !138892 (merged).

Related to #409884 (closed)

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