x/playground: in About text, document that vet is used

[meirf]

Now that vet is included in playground Run, the About text should mention it.

Current:

The service receives a Go program, compiles, links, and runs the program inside a sandbox, then returns the output.

Maybe something like "... receives a Go program, compiles, links, vets and runs the program inside a sandbox..."

@ysmolsky

One counterargument is that "go vet" is a pretty unique search query and goes straight to https://golang.org/cmd/vet anyway.

[ysmolski]

I think we should do this. Preparing the patch.

[gopherbot]

Change https://golang.org/cl/140497 mentions this issue: playground: mention vet in about text

[dmitshur]

I've deployed the new version. Thanks @ysmolsky!