[docs] make visual studio code section more precise

Summary: removed an unnecessary sentence and changed VSCode to Visual Studio Code

Test Plan: docs

Reviewers: geekbrother, atul, ashoat

Reviewed By: atul, ashoat

Subscribers: ashoat, palys-swm, Adrian, karol-bisztyga, benschac, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3603