internal/testing/sample: use AddPackage in LegacyDefaultModule

For golang/go#39629

Change-Id: If017c090b179554cd7c05177c941e1c1765f6139
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/263216
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
diff --git a/internal/testing/sample/legacy.go b/internal/testing/sample/legacy.go
index 431675f..d7f4b19 100644
--- a/internal/testing/sample/legacy.go
+++ b/internal/testing/sample/legacy.go
@@ -39,9 +39,7 @@
 }
 
 func LegacyDefaultModule() *internal.Module {
-	return LegacyAddPackage(
-		LegacyModule(ModulePath, VersionString),
-		LegacyPackage(ModulePath, Suffix))
+	return AddPackage(LegacyModule(ModulePath, VersionString), ModulePath+"/"+Suffix)
 }
 
 // LegacyModule creates a Module with the given path and version.