internal/postgres: replace LegacyPackage in TestGetImportedBy

For golang/go#39629

Change-Id: I3d52d4af80125cd70398301011a664f812ee0ccd
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/262758
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>

internal/postgres/details_test.go

diff --git a/internal/postgres/details_test.go b/internal/postgres/details_test.go
index 2e89172..ccd4dbc 100644
--- a/internal/postgres/details_test.go
+++ b/internal/postgres/details_test.go
@@ -217,17 +217,13 @@
 		m3          = sample.LegacyModule("path3.to/foo", "v1.3.0", "bar3")
 		testModules = []*internal.Module{m1, m2, m3}
 
-		pkg1 = m1.LegacyPackages[0]
-		pkg2 = m2.LegacyPackages[0]
-		pkg3 = m3.LegacyPackages[0]
+		pkg1 = m1.Packages()[0]
+		pkg2 = m2.Packages()[0]
+		pkg3 = m3.Packages()[0]
 	)
-
 	pkg1.Imports = nil
 	pkg2.Imports = []string{pkg1.Path}
 	pkg3.Imports = []string{pkg2.Path, pkg1.Path}
-	m1.Units[1].Imports = pkg1.Imports
-	m2.Units[1].Imports = pkg2.Imports
-	m3.Units[1].Imports = pkg3.Imports
 
 	for _, tc := range []struct {
 		name, path, modulePath, version string