small README edits

[JoeGermuska]

Privilege warnings

interactive-textbook/README.md

Line 20 in 15b359f

Desktop, VS Code, and the course. Partway through, Docker Desktop may ask for a few approvals.

I was also asked for privileges by Terminal and VS Code:

old code

interactive-textbook/README.md

Lines 29 to 31 in 15b359f

	## Old files
	py-dataviz is an old folder that supported Jupyter Lab for Python. Jupyter Lab is not included in the current setup.

Is there a reason not to just remove it from the repository?

early "open"

I think that the installer opened the "home page" in VS Code before it was done installing. I wasn't paying close attention, so it's possible that I opened it accidentally myself.

[graceeshao]

I retested and also got the early open. In the install commands, the VS Code extensions (dev container and knight lab) were being installed alongside VS Code (before the Docker build step), which may have launched VS Code as a side effect. The extension would then activate and try to reopen in a container that wasn't ready yet. Moved both extension installs to be after the Docker build completes, so hopefully this is a fix. Also updated readme to reflect these privileges and removed old files.