openjfx: 17.0.11+3 -> 21.0.3+2

openjfx17 requires gradle_7, which is EOL and marked insecure. This is a
pretty good argument for not leaving the default openjfx pointing to
openjfx17.

pkgs/by-name/op/openjfx/package.nix

@@ -1,5 +1,5 @@
 {
-  featureVersion ? "17",
+  featureVersion ? "21",
 
   lib,
   stdenv,

pkgs/top-level/all-packages.nix

@@ -4780,8 +4780,8 @@ with pkgs;
     inherit (emacs.pkgs.melpaStablePackages) irony;
   };
 
-  openjfx17 = openjfx;
-  openjfx21 = callPackage ../by-name/op/openjfx/package.nix { featureVersion = "21"; };
+  openjfx17 = callPackage ../by-name/op/openjfx/package.nix { featureVersion = "17"; };
+  openjfx21 = openjfx;
   openjfx25 = callPackage ../by-name/op/openjfx/package.nix { featureVersion = "25"; };
 
   openjdk8-bootstrap = javaPackages.compiler.openjdk8-bootstrap;