RFR: 8327482: Fix missing image resource in HelloImage toy app

[Lukasz Kostyra]

Replaced existing `slowImageURL` address to a new image (+ some extra bits related to it). Image has been taken from open-source repository of Duke images and licensed under BSD license: https://wiki.openjdk.org/display/duke/Gallery

-------------

Commit messages:
 - Change slow image link to new one

Changes: https://git.openjdk.org/jfx/pull/1410/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1410&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327482
  Stats: 4 lines in 1 file changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1410.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1410/head:pull/1410

PR: https://git.openjdk.org/jfx/pull/1410