Switch to Amazon Corretto because it bundles Java FX.

.travis.yml

@@ -59,6 +59,8 @@ before_script:
     fi
   - if [ $TRAVIS_OS_NAME = "osx" ]; then
         export PATH=${PATH}:/usr/local/opt/gettext/bin;
+        brew uninstall java --force;
+        brew cask uninstall java --force;
     fi
 
 script: