PR: Fix link to Spyder docs in connect to external kernel dialog

[CAM-Gerlach]

Description of Changes

As helpfully spotted by @hyamanieu in spyder-ide/spyder-docs#297 , the URL to the external kernel docs in the Connect to kernel dialog is out of date and doesn't work. This PR fixes that. I also checked all the other URLs to the docs, and confirmed the rest are all up to date and working.

Affirmation

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[CAM-Gerlach]

Note: @ccordoba12 when merging to master, you'll likely want to change the 5 in the link to current; the 5 makes sure it stays locked to the correct version of the docs even in old versions of Spyder, so the links don't suddenly break with changes in current.

[ccordoba12]

when merging to master, you'll likely want to change the 5 in the link to current

Good point! Will take care of it.

[ccordoba12]

Thanks @CAM-Gerlach!

[CAM-Gerlach]

Thanks @ccordoba12 .