Bump the dependencies group with 4 updates

Bumps the dependencies group with 4 updates: org.openjfx:javafx-fxml, org.openjfx:javafx-controls, org.openjfx:javafx-graphics and [org.apache.maven.plugins:maven-javadoc-plugin](https://github.com/apache/maven-javadoc-plugin).


Updates `org.openjfx:javafx-fxml` from 20.0.2 to 21

Updates `org.openjfx:javafx-controls` from 20.0.2 to 21

Updates `org.openjfx:javafx-graphics` from 20.0.2 to 21

Updates `org.apache.maven.plugins:maven-javadoc-plugin` from 3.5.0 to 3.6.0
- [Release notes](https://github.com/apache/maven-javadoc-plugin/releases)
- [Commits](apache/maven-javadoc-plugin@maven-javadoc-plugin-3.5.0...maven-javadoc-plugin-3.6.0)

---
updated-dependencies:
- dependency-name: org.openjfx:javafx-fxml
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dependencies
- dependency-name: org.openjfx:javafx-controls
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dependencies
- dependency-name: org.openjfx:javafx-graphics
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dependencies
- dependency-name: org.apache.maven.plugins:maven-javadoc-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -21,7 +21,7 @@
         <maven-compiler-plugin.version>3.11.0</maven-compiler-plugin.version>
         <maven-dependency-plugin.version>3.1.1</maven-dependency-plugin.version>
         <maven-gpg-plugin>3.1.0</maven-gpg-plugin>
-        <maven-javadoc-plugin.version>3.5.0</maven-javadoc-plugin.version>
+        <maven-javadoc-plugin.version>3.6.0</maven-javadoc-plugin.version>
         <maven-javafx-plugin>0.0.8</maven-javafx-plugin>
         <maven-nexus-staging-plugin>1.6.13</maven-nexus-staging-plugin>
         <maven-release-plugin.version>3.0.1</maven-release-plugin.version>
@@ -31,7 +31,7 @@
         <commons-lang.version>3.13.0</commons-lang.version>
         <configurable.version>0.34</configurable.version>
         <logback.version>1.4.11</logback.version>
-        <openjfx.version>20.0.2</openjfx.version>
+        <openjfx.version>21</openjfx.version>
         <FROST-Client.version>0.44</FROST-Client.version>
     </properties>