update JavaFX

javafx/Dockerfile

@@ -1,11 +1,15 @@
 FROM gtcs2110/autograder-base:1.11.0
 
-# Install OpenJDK 17 with JavaFX along with dummy X server
+# Install OpenJDK 17 along with dummy X server
+#
+# Despite this Docker container being called "autograder-base-javafx",
+# It doesn't install JFX. (It's okay, the wrong JavaFX was being installed anyway).
+# This container installs the display servers that will allow JavaFX programs to be run.
 RUN apt-get update \
     && apt-get install --no-install-recommends -y \
         xserver-xorg-video-dummy \
-        java-common openjdk-17-jdk openjfx \
-        libgl1-mesa-glx libxi6 libxtst6 libgtk2.0-0 libatk1.0-0 libpango1.0-0 libgdk-pixbuf2.0-0 libcairo2
+        java-common openjdk-21-jdk \
+        libgl1-mesa-glx libxi6 libxtst6 libgtk-3-0 libatk1.0-0 libpango1.0-0 libgdk-pixbuf2.0-0 libcairo2
 
 # Cleanup
 RUN rm -rf /tmp/pkgs && apt-get clean