Fix documentation for cpu and memory usage metrics

[lucasmo]

Fix incorrect documentation for metrics are reported in airflow/task/task_runner/standard_task_runner.py. The documentation suggests that "percent" is in the metric names when it is not.

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[boring-cyborg]

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[shalberd]

@potiuk @thesuperzapper this seems like something very straight-forward and intuitive; can it not be reviewed, accepted, and merged?

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[potiuk]

Can you please create a backport as a (cherry-pick -x PR to v2-10-test if you want this released in 2.10 please ) @shalberd @lucasmo - otherwise it will only be released in Airflow 3 (and I am going for holidays now so I won't have time for it).

[vincbeck]

Backport in v2-10-test: #42256