Remove redundant setting of DistFiles by apexBundle

A previous change handles dist properties automatically for all module
types and as a result has made the apexBundle setting of DistFiles
redundant so this change removes that.

Test: m nothing
      m dist sdk - before and after this change, compare result to
      make sure that there are no significant differences.
      Test the effect on the apex by following instructions in
      http://b/172951145
Bug: 174226317
Change-Id: If6f741b5b73b3335f4c478a6528f5f311cd633e4

apex/androidmk.go

@@ -334,7 +334,6 @@ func (a *apexBundle) writeRequiredModules(w io.Writer) {
 
 func (a *apexBundle) androidMkForType() android.AndroidMkData {
 	return android.AndroidMkData{
-		DistFiles: a.distFiles,
 		Custom: func(w io.Writer, name, prefix, moduleDir string, data android.AndroidMkData) {
 			moduleNames := []string{}
 			apexType := a.properties.ApexType