flatpak: switch URL to invent and newer tag

1 job for master in 4 minutes and 55 seconds
Status Job ID Name Coverage
  Build
failed #52143
flatpak
flatpak

00:04:55

 
Name Stage Failure
failed
flatpak Build
-- 
* ECM (required version >= 5.70.0), Extra CMake Modules., <https://commits.kde.org/extra-cmake-modules>

-- Configuring incomplete, errors occurred!
See also "/run/build/kdelibs4support/_flatpak_build/CMakeFiles/CMakeOutput.log".
Error: module kdelibs4support: Child process exited with code 1
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1