fix: Add Compability for JDK 11

[wba2hi]

This issue is a bit harder to reproduce locally. The following steps are necessary:

1. Setup jenv for easy switching to different jdk versions
2. Install openjdk17 and openjdk21
3. Register openjdk17 and openjdk21 using jenv add ...
4. open a terminal and switch to the project folder
5. use jenv local 21 to use jdk21 for building the project
6. execute ./gradlew clean build (the vss-processor-plugin here is now only supporting >= jdk 21 without the fix being applied; if build with jdk 17 it would be only supporting >= jdk 17)
7. publish the artifact to mavenLocal (a few lines of code need to be adapted in code)
8. change the samples to use the mavenLocal version and add mavenLocal to the plugin repositories
9. execute jenv local 17 to switch to jdk17 for building the project
10. execute ./gradlew clean build

Depending on if the fix was applied or not, an error message will be shown.

[lukasmittag]

LGTM