Fix usage_data.rb yard tag for track_usage_event

What does this MR do and why?

The yard @param tag for Gitlab::Utils::UsageData#track_usage_event is incorrect, it accepts a Symbol as well as a String.

This causes false positive Code Inspect errors in RubyMine for code which calls this method.

Screenshots or screen recordings

How to set up and validate locally

Open ee/app/graphql/mutations/remote_development/workspaces/update.rb and see that RubyMine Inspect Code no longer shows the above error.

MR acceptance checklist

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