Remove clearEncryptionPassword() from LockPatternUtils

Remove this method which cleared the FDE password, since is no longer
used.  It was only being used by the accessibility settings in the
Settings app, and that caller was removed by http://ag/16624515.

Bug: 208476087
Change-Id: If0c75774555d3503f21857e66cce527c5edfa586

core/java/com/android/internal/widget/LockPatternUtils.java

@@ -769,17 +769,6 @@ public class LockPatternUtils {
         return StorageManager.isFileEncryptedNativeOrEmulated();
     }
 
-    /**
-     * Clears the encryption password.
-     */
-    public void clearEncryptionPassword() {
-        try {
-            getLockSettings().updateEncryptionPassword(StorageManager.CRYPT_TYPE_DEFAULT, null);
-        } catch (RemoteException e) {
-            Log.e(TAG, "Couldn't clear encryption password");
-        }
-    }
-
     /**
      * Retrieves the quality mode for {@code userHandle}.
      * @see DevicePolicyManager#getPasswordQuality(android.content.ComponentName)