Revert "Filesystem modules follow the installation semantic"

Revert submission 3066748-duplicate_entry_fs

Reason for revert: b/338159248

Reverted changes: /q/submissionid:3066748-duplicate_entry_fs

Change-Id: I8aacdb36efce8343c3713542eee209e71bde660b
diff --git a/filesystem/system_image.go b/filesystem/system_image.go
index 15cacfb..5028a49 100644
--- a/filesystem/system_image.go
+++ b/filesystem/system_image.go
@@ -98,5 +98,5 @@
 // Note that "apex" module installs its contents to "apex"(fake partition) as well
 // for symbol lookup by imitating "activated" paths.
 func (s *systemImage) filterPackagingSpec(ps android.PackagingSpec) bool {
-	return s.filesystem.filterInstallablePackagingSpec(ps) && ps.Partition() == "system"
+	return ps.Partition() == "system"
 }