chore: Update freedesktop runtime to 23.08

.gitlab-ci.yml

@@ -86,7 +86,7 @@ pages:
   tags:
     - flatpak
   script:
-    - flatpak install --user --noninteractive org.freedesktop.Sdk.Extension.rust-nightly//23.08beta
+    - flatpak install --user --noninteractive org.freedesktop.Sdk.Extension.rust-nightly//23.08
     - sed -i 's|rust-stable|rust-nightly|g' ${MANIFEST_PATH}
     - flatpak-builder --keep-build-dirs --user --disable-rofiles-fuse --stop-at=${FLATPAK_MODULE} flatpak_app --repo=repo ${BRANCH:+--default-branch=$BRANCH} ${MANIFEST_PATH}
     - echo "ninja src/doc" | flatpak-builder --disable-rofiles-fuse --build-shell=${FLATPAK_MODULE} flatpak_app ${MANIFEST_PATH}

CONTRIBUTING.md

@@ -37,10 +37,10 @@ flatpak remote-add --user --if-not-exists gnome-nightly https://nightly.gnome.or
 flatpak install --user gnome-nightly org.gnome.Sdk//master org.gnome.Platform//master
 
 # Install the required rust-stable extension from Flathub
-flatpak install --user flathub org.freedesktop.Sdk.Extension.rust-stable//23.08beta
+flatpak install --user flathub org.freedesktop.Sdk.Extension.rust-stable//23.08
 
 # Install the required llvm extension from Flathub
-flatpak install --user flathub org.freedesktop.Sdk.Extension.llvm16//23.08beta
+flatpak install --user flathub org.freedesktop.Sdk.Extension.llvm16//23.08
 ```
 
 If you are building the flatpak manually you will also need flatpak-builder on your system, or the