cmd/cover: add newline to fix -covermode=atomic build error
Fix a minor buglet in atomic mode fixup that would generate
non-compilable code for a package containing only the "package X"
clause with no trailing newline following the "X".
Fixes #58370.
Change-Id: I0d9bc4f2b687c6bd913595418f6db7dbe50cc5df
Reviewed-on: https://go-review.googlesource.com/c/go/+/466115 Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>