go/packages/packagestest: fold modules_111.go into modules.go

x/tools hasn't supported Go versions earlier than 1.11 (or even 1.11
itself) for a while.

Change-Id: I723c43dbcd1c4df56d8c663a78ec31524b912985
Reviewed-on: https://go-review.googlesource.com/c/tools/+/581795
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

go/packages/packagestest/export.go

@@ -147,7 +147,7 @@ type Exporter interface {
 
 // All is the list of known exporters.
 // This is used by TestAll to run tests with all the exporters.
-var All []Exporter
+var All = []Exporter{GOPATH, Modules}
 
 // TestAll invokes the testing function once for each exporter registered in
 // the All global.

go/packages/packagestest/gopath.go

@@ -41,10 +41,6 @@ import (
 //	/sometemporarydirectory/repoa/src
 var GOPATH = gopath{}
 
-func init() {
-	All = append(All, GOPATH)
-}
-
 type gopath struct{}
 
 func (gopath) Name() string {

go/packages/packagestest/modules.go

@@ -18,7 +18,7 @@ import (
 )
 
 // Modules is the exporter that produces module layouts.
-// Each "repository" is put in it's own module, and the module file generated
+// Each "repository" is put in its own module, and the module file generated
 // will have replace directives for all other modules.
 // Given the two files
 //