cmd: update version ref.

[imhardikj]

Fixes #1635

• Updates version ref.

[jorgeorpinel]

Good so far @imhardikj! Left some specific comments above.

But also, it feels like it needs more updates (keep in mind this is a pretty old doc.) Some possible issues I noticed after a quick readthrough:

• Rewrite "Official release": Not sure why the paragraph starts with "These instructions..." — should start by explaining what the official release (number) is.
• Link to https://www.pypa.io/ ?
• In "Development version", should there be a pip install... code block that doesn't correspond to the instructions in https://dvc.org/doc/user-guide/contributing/core#development-environment? (Maybe just link there).
• "In our case, we use PyInstaller..." should be a note, I think (block quote).

[jorgeorpinel]

Almost there (I hope).

• A few grammar typos left which are worrying — I have to read everything very carefully to make sure the sentence articles are there which makes it harder to review your changes. Usually this is not something we have to worry about. Please pay 3x attention to this going forward.
• The description of Development version needs a little more work, but that's the last of it.
• I took care of another few things so this is closer to merge.

Thanks @imhardikj

[jorgeorpinel]

Done! Just a couple small copy edits pending ☝️ (I may take care of them).

[jorgeorpinel]

Thanks again @imhardikj, let's keep moving on the remaining cmd ref updates from v0 to v1. I'll keep the reviews more focused and create separate issues if deeper text reviews are needed.