MNT: Updates to conda recipe

Hi Istvan,

Would you be able to update the TIRL conda recipe to fix a few small issues for getting TIRL into FSL 6.0.4:

1. Link to, rather than move, the TIRL data directory from $FSLDIR - the root conda environment will cache the un-tarred TIRL package, and modifying it by removing the data directory can cause conda to complain about it being corrupted.

2. Do not invoke python or conda from post-link.sh, as there is no guarantee that they are the python/conda commands associated with the environment into which TIRL is being installed. Furthermore, running python -c "import tirl..." may have unintended side effects^*. I've replaced your python invocations with sed, and have removed the line which sets up the $TIRLHOME environment variable. From what I could see, $TIRLHOME is not actually used anywhere, and it would be easiest if we could just omit it for the time being.

3. Clean up installed data in the pre-unlink.sh script.

4. Renamed the conda-recipies directory, to get rid of the typo in the name.

Thanks!

^*For example: https://git.fmrib.ox.ac.uk/ihuszar/tirl/-/blob/master/src/tirl/settings.py#L26 . As an aside, I would suggest that you use the built-in tempfile module, rather than hard-coding /tmp/TIRLTWD, because the temporary directory is not guaranteed to be located at /tmp/, so this call may not succceed in all environments.