Rename FixturePreparers to GroupFixturePreparers

FixturePreparers is a bad name for a method that creates a collection
of FixturePreparers for a couple of reasons:
* Conventionally it would be used as the name for []FixturePreparer if
  it is necessary to add behavior to that.
* There are many different types of collection, particularly when order
  matters.

Bug: 181070625
Test: m nothing
Change-Id: I55394ff369375dcac2d7b72e4d803a4818762d36
diff --git a/android/fixture_test.go b/android/fixture_test.go
index 7bc033b..5a7bf3b 100644
--- a/android/fixture_test.go
+++ b/android/fixture_test.go
@@ -32,9 +32,9 @@
 	preparer3 := appendToList("preparer3")
 	preparer4 := appendToList("preparer4")
 
-	preparer1Then2 := FixturePreparers(preparer1, preparer2)
+	preparer1Then2 := GroupFixturePreparers(preparer1, preparer2)
 
-	preparer2Then1 := FixturePreparers(preparer2, preparer1)
+	preparer2Then1 := GroupFixturePreparers(preparer2, preparer1)
 
 	buildDir := "build"
 	factory := NewFixtureFactory(&buildDir, preparer1, preparer2, preparer1, preparer1Then2)