Unconditionally disable reductions for hipSYCL

[fknorr]

hipSYCL aka AdaptiveCpp has recently merged reduction support which is not 1:1 compatible with an earlier attempt to implement the API (now defunct), which we were detecting in CMake to conditionally expose it in Celerity.

This PR removes the check and unconditionally disables reduction support on hipSYCL for now to unblock CI. It will be re-enabled as part of the final IDAG merge when all accompanying issues have been resolved.

This PR also silences a deprecation warning to avoid bumping the minimum hipSYCL version.

[github-actions[bot]]

Check-perf-impact results: (7b849de16ff11660b98988ab0b032db7)

:question: No new benchmark data submitted. :question:
Please re-run the microbenchmarks and include the results if your commit could potentially affect performance.

[coveralls]

Pull Request Test Coverage Report for Build 9543852448

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 94.744%

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Totals
Change from base Build 9205581023:	0.0%
Covered Lines:	6873
Relevant Lines:	7072

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💛 - Coveralls