doc: move v8.stopCoverage() to expected location in doc

PR-URL: https://github.com/nodejs/node/pull/39212


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Harshitha K P <harshitha014@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>