Update editable_packages.rst

[nowgain-nowpain]

correct typo

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[uilianries]

@nowgain-nowpain Thank you for your contribution, please, sign the CLA first, so we can approve your fix.