Revert "cmd/goimports: return exit code 1 when -l finds files to change"

This reverts CL 234484/commit e641245118.

Reason for revert: Incompatible behavior change.

Change-Id: I82216a2a352e6da62d1a09e47b3774d52527effc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/237378
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Khosrow Moossavi <khos2ow@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

cmd/goimports/goimports.go

@@ -154,7 +154,6 @@ func processFile(filename string, in io.Reader, out io.Writer, argType argumentT
 		// formatting has changed
 		if *list {
 			fmt.Fprintln(out, filename)
-			exitCode = 1
 		}
 		if *write {
 			if argType == fromStdin {