Revert "Detect system_ext provenance for APKs-in-APEX"

This reverts commit abf29541e5.

Reason for revert: This breaks wembley boot, as TreeHugger repeatedly pointed out on this CL, and which was ignored.
Bug: 205967276

Change-Id: Ic5ecc257ec79a759d124da459e0fb584f62c471b

services/core/java/com/android/server/pm/InitAndSystemPackageHelper.java

@@ -152,7 +152,7 @@ final class InitAndSystemPackageHelper {
         for (int i = 0, size = SYSTEM_PARTITIONS.size(); i < size; i++) {
             ScanPartition sp = SYSTEM_PARTITIONS.get(i);
             if (apexInfo.preInstalledApexPath.getAbsolutePath().startsWith(
-                    sp.getFolder().getAbsolutePath() + File.separator)) {
+                    sp.getFolder().getAbsolutePath())) {
                 return new ScanPartition(apexInfo.apexDirectory, sp, SCAN_AS_APK_IN_APEX);
             }
         }