Revert "Add Build.isAtLeastO"

This reverts commit 3b8b07c8f4.

Bug: 32668621
Test: this is a revert, no original tests
Change-Id: I893025f32423aed3fe15a64c22753d24aafc4e65

core/java/android/app/BackStackRecord.java

@@ -349,7 +349,9 @@ final class BackStackRecord extends FragmentTransaction implements
 
     public BackStackRecord(FragmentManagerImpl manager) {
         mManager = manager;
-        mAllowOptimization = Build.isAtLeastO();
+        int targetSdkVersion = manager.mHost.getContext().getApplicationInfo().targetSdkVersion;
+        // TODO: make the check N_MR1 or O
+        mAllowOptimization = targetSdkVersion > Build.VERSION_CODES.N;
     }
 
     public int getId() {

core/java/android/os/Build.java

@@ -924,16 +924,4 @@ public class Build {
             return -1;
         }
     }
-
-    /**
-     * Check if the device is running on the Android O release or newer.
-     *
-     * @return {@code true} if O APIs are available for use
-     *
-     * @hide
-     */
-    public static boolean isAtLeastO() {
-        return !"REL".equals(VERSION.CODENAME)
-                && "O".compareTo(VERSION.CODENAME) <= 0;
-    }
 }