_lint_ flags things for _OmitExplicitReturns_ but _format_ doesn't fix them

[thomasvl]

With a dummy test file:

var f = l.filter { return $0.a != o }

And a config file that includes:

    "OmitExplicitReturns" : true,

swift format lint --configuration swift-format.cfg test.swift

Produces:

test.swift:1:20: warning: [OmitExplicitReturns] 'return' can be omitted because body consists of a single expression

However

swift format format --configuration swift-format.cfg test.swift

Doesn't actually return the return in what it produces.

[ahoppen]

Synced to Apple’s issue tracker as rdar://136555297