Do NOT do this. Do not attract attention to something that is very very common on senior year transcripts (and especially not with such an “excuse”.)
You already have a solid schedule. Adcoms aren’t going to spend hours wondering about the extra class you dropped or about the reason (if they devote 2 seconds of thought to it, they’ll assume it’s the most likely reason for a senior year schedule change: student realized had taken more than could chew, ie., good self awareness.) Your transcript will have been reformated so that it looks exactly like all other schedules adcoms read at that college - for all you know depending on the software they use, the drop won’t even appear- and they’ll spend 2-3mn checking it. Wondering about a dropped class isn’t going to be anywhere near their top elements to check.
The rest of the above advice is good though. Especially wrt mental health.