Removal of unused methods AppendProperties and PrependProperties from topDownMutatorContext

Test: m nothing
Bug: n/a

Change-Id: Ia37d1c9b96c39603964ba8db2ea6ba52d1138472
diff --git a/android/module.go b/android/module.go
index 767f9f4..b500f01 100644
--- a/android/module.go
+++ b/android/module.go
@@ -1300,6 +1300,8 @@
 
 func (m *ModuleBase) DepsMutator(BottomUpMutatorContext) {}
 
+// AddProperties "registers" the provided props
+// each value in props MUST be a pointer to a struct
 func (m *ModuleBase) AddProperties(props ...interface{}) {
 	m.registerProps = append(m.registerProps, props...)
 }