Fix markdown in documentation in 'Manually specifying an interpreter'

[DonJayamanne]

The markdown doesn't seem to be correctly formatted:
https://code.visualstudio.com/docs/python/environments#_manually-specifying-an-interpreter

[gaurikholkar-zz]

Can I pick this up?

[DonJayamanne]

Anyone can pick an issue and submit a PR. specially those takes with 'Good first issue'.
So to answer your question, most certainly yes.

[brettcannon]

Sorry, @gaurikholkar , but we went ahead and fixed this while dealing with other doc bugs that were in the same file.

Fixed in microsoft/vscode-docs#1350 .