remove .vscode and gitignore it (#4498)

**What type of PR is this?**

Other

**What does this PR do? Why is it needed?**

The .vscode directory isn't meant to be checked in like this, and causes
churn that vscode users have to remove before sending PRs. We remove it,
add it to .gitignore so future folks don't accidentally check it in.
Folks can check out the more general Editor setup wiki page for
instructions.

**Which issues(s) does this PR fix?**

Fixes #4497.