Comment usb_serial_jtag_ll_txfifo_flush()

[Jason2866]

Patch PR #9401 with the change from #9378 (comment)

@SuGlider

[github-actions]

	Warnings
⚠️	Some issues found for the commit messages in this PR: the commit message "Comment usb_serial_jtag_ll_txfifo_flush() -> https://github.com/espressif/arduino-esp32/issues/9378#issuecomment-2013740414": summary looks empty type/action looks empty Please fix these commit messages - here are some basic tips: follow Conventional Commits style correct format of commit message should be: <type/action>(<scope/component>): <summary>, for example fix(esp32): Fixed startup timeout issue allowed types are: change,ci,docs,feat,fix,refactor,remove,revert,test sufficiently descriptive message summary should be between 20 to 72 characters and start with upper case letter avoid Jira references in commit messages (unavailable/irrelevant for our customers) TIP: Install pre-commit hooks and run this check when committing (uses the Conventional Precommit Linter).
⚠️	The **target branch** for this Pull Request **must be the default branch** of the project (`master`). If you would like to add this feature to a different branch, please state this in the PR description and we will consider it.

👋 Hello Jason2866, we appreciate your contribution to this project!

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[SuGlider]

It fails with the test case that I have provided in the PR.
S3 and C3 are hanging after about 50 transmissions.

[Jason2866]

Closing since does introduce new issues.