LFRic Rose-Stem with Cylc 8.4

[James Bruten (james-bruten-mo)]

The met office cylc version has just been updated to 8.4. This includes a change to the rose-stem lint checker which means that the lfric rose-stem suite no longer passes this test. This will affect all branches already made. Feel free to ignore that test for the current release cycle or run export CYLC_VERSION=cylc-8.3.6-1 before launching rose-stem.