Fix documentation bug with METADATA_KEY_LOCATION

MPEG4Writer::writeGeoDataBox() has always written latitude
before longitude since it was introduced. And the ISO-6709
is also to have +-{latitude}+-{longitude}/ so we should have
the correct information here.

This is likely to be important for Q since lat/long are no
longer accessible via MediaStore.

Bug: 134100244
Test: documentation change only
Change-Id: If157e3b0a639da9e012c0dd23fcfacfa0a59c28e

media/java/android/media/MediaMetadataRetriever.java

@@ -869,7 +869,7 @@ public class MediaMetadataRetriever implements AutoCloseable {
      * This key retrieves the location information, if available.
      * The location should be specified according to ISO-6709 standard, under
      * a mp4/3gp box "@xyz". Location with longitude of -90 degrees and latitude
-     * of 180 degrees will be retrieved as "-90.0000+180.0000", for instance.
+     * of 180 degrees will be retrieved as "+180.0000-90.0000/", for instance.
      */
     public static final int METADATA_KEY_LOCATION        = 23;
     /**