Bump TIGRE version

[JeppeKlitgaard]

CIL currently uses a rather old TIGRE version (2.6). This should be updated and may be required by #1915.

TIGRE have just cut a new release with CIL in mind which should simplify the building of our own conda package of TIGRE (see: CERN/TIGRE#708), which is handled in https://github.com/TomographicImaging/TIGRE-conda

Blocked by: TomographicImaging/TIGRE-conda#16 (ready for review)
Blocks: #1915

[JeppeKlitgaard]

I have done this and tested in my pixi-experiment environment and there are some TIGRE tests that are failing