chore(flatpak): don't bundle JREs

After https://github.com/PrismLauncher/PrismLauncher/pull/2069, JREs can
be managed at runtime. This is great for the Flatpak, as previously
*all* JREs had to be installed and could not be updated independently of
the launcher's Flatpak. It also makes using unsupported Java versions
easier as the launcher can download any version in the sandbox

We don't need to include these anymore

Signed-off-by: seth <getchoo@tuta.io>

flatpak/org.prismlauncher.PrismLauncher.yml

@@ -3,9 +3,7 @@ runtime: org.kde.Platform
 runtime-version: 6.7
 sdk: org.kde.Sdk
 sdk-extensions:
-  - org.freedesktop.Sdk.Extension.openjdk21
   - org.freedesktop.Sdk.Extension.openjdk17
-  - org.freedesktop.Sdk.Extension.openjdk8
 
 command: prismlauncher
 finish-args:
@@ -43,19 +41,6 @@ modules:
       - type: dir
         path: ../
 
-  - name: openjdk
-    buildsystem: simple
-    build-commands:
-      - mkdir -p /app/jdk/
-      - /usr/lib/sdk/openjdk21/install.sh
-      - mv /app/jre /app/jdk/21
-      - /usr/lib/sdk/openjdk17/install.sh
-      - mv /app/jre /app/jdk/17
-      - /usr/lib/sdk/openjdk8/install.sh
-      - mv /app/jre /app/jdk/8
-    cleanup:
-      - /jre
-
   - name: glfw
     buildsystem: cmake-ninja
     config-opts: