5082749: GIF stream metadata specification of aspect ratio is incorrect

Reviewed-by: bae, prr
Contributed-by: NVadim Pakhnushev <vadim.pakhnushev@oracle.com>

src/share/classes/javax/imageio/metadata/doc-files/gif_metadata.html

@@ -90,7 +90,7 @@ images that do not have their own local color table.
         <!-- Max value: 8 (inclusive) -->
       <!ATTLIST "LogicalScreenDescriptor" "pixelAspectRatio" #CDATA
          #REQUIRED>
-        <!-- If 0, indicates square pixels, else W/H = (value + 16)/64 -->
+        <!-- If 0, indicates square pixels, else W/H = (value + 15)/64 -->
         <!-- Data type: Integer -->
         <!-- Min value: 0 (inclusive) -->
         <!-- Max value: 255 (inclusive) -->