[Chapel Merge] Update technote about current limitations with GPU

Branch: refs/heads/main
Revision: 23dc696
Author: stonea
Link: Unavailable
Log Message:

Merge pull request #19344 from stonea/update_gpu_tech_notes

Update technote about current limitations with GPU support

Update tech note to list limitations based on a comment (we now support functions calls in GPU loops): #19333 (comment) and also that we don't support any CHPL_COMM except 'none' (as described here: #18850).

[Reviewed by @daviditen]

Modified Files:
M doc/rst/technotes/gpu.rst

Compare: https://github.com/chapel-lang/chapel/compare/3d2e1719fa00...23dc69653b68