fix end function when piping on request

[aaharu]

Checklist

rework of https://github.com/ladjs/supertest/pull/742

• [x] I have ensured my pull request is not behind the main or master branch of the original repository.
• [x] I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
• [ ] I have written a commit message that passes commitlint linting.
• [x] I have ensured that my code changes pass linting tests.
• [x] I have ensured that my code changes pass unit tests.
• [x] I have described my pull request and the reasons for code changes along with context if necessary.

[thehenrymcintosh]

I'm also having this issue - thank you for the fix @aaharu