Flathub JDK SDKs broken

Installing the JDK from Flathub (for example https://flathub.org/apps/org.freedesktop.Sdk.Extension.openjdk21) and then running Flatpak VSCode with `FLATPAK_ENABLE_SDK_EXT=openjdk21 flatpak run com.visualstudio.code` as per the instructions on flatpak-warning.txt does not work with Java. The file is inaccessible because of the sandbox. Please loosen the sandbox a little to be able to view the JDK binary. See more here: https://github.com/redhat-developer/vscode-java/issues/510