Add grid alternative for de_tlbg_thueringen_NTv2gridTH.tif

[jjimenezshaw]

related: OSGeo/PROJ-data#128

[rouault]

@kbevers Will you be in a mood of release a PROJ-data 1.20 together with PROJ 9.5.1 with that referenced grid, and so this should be backported, or is it 9.6.0 material ? (and if we do backport, do we need to update the PROJ.DATA.VERSION item in data/sql/metadata.sql while we are it, or will you do per the release procedure, as documented ?)

[kbevers]

Will you be in a mood of release a PROJ-data 1.20 together with PROJ 9.5.1 with that referenced grid, and so this should be backported, or is it 9.6.0 material ?

No worries, there's often a PROJ-data release bundled with patch releases of PROJ.

do we need to update the PROJ.DATA.VERSION item in data/sql/metadata.sql while we are it, or will you do per the release procedure, as documented ?

I don't mind bumping PROJ.DATA.VERSION now, it's easy to gloss over it during the release procedure. I usually check it and am most times delighted to see that's already been done by someone thinking ahead :)

[rouault]

I don't mind bumping PROJ.DATA.VERSION now

done