Test: Remove broken TEST_EVERYTHING branch from P0896R4_views_elements

[zika (tycket033-tech)]

Fixes #6237.

This removes the TEST_EVERYTHING branch from P0896R4_views_elements.

That branch tries to instantiate proxy-reference ranges, but those references aren't tuple-like and can't satisfy elements_view's constraints. The existing explicit matrix already covers the relevant non-proxy combinations, so it now runs regardless of whether TEST_EVERYTHING is defined.

Validation:

• Built and ran P0896R4_views_elements normally with /W4 /WX.
• Built and ran it again with /DTEST_EVERYTHING /W4 /WX.
• Both configurations passed.

AI disclosure: OpenAI Codex with GPT-5.6 Sol was used to inspect the issue and apply this four-line test-only deletion. I reviewed the final diff and test results before submission.

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[Stephan T. Lavavej (StephanTLavavej)]

Thanks. This PR should have been created normally, instead of in draft status (which for us, doesn't run checks; not that it makes a difference for first-time contributor PRs which can't automatically run checks).

[Copilot]

Pull request overview

Removes an invalid TEST_EVERYTHING path while preserving the valid non-proxy elements_view test matrix.

Changes:

• Always runs the explicit non-proxy range permutations.
• Prevents unsupported proxy-reference instantiations.

Show a summary per file

File	Description
tests/std/tests/P0896R4_views_elements/test.cpp	Removes the broken conditional test branch.

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[zika (tycket033-tech)]

Thanks. This PR should have been created normally, instead of in draft status (which for us, doesn't run checks; not that it makes a difference for first-time contributor PRs which can't automatically run checks).

Thanks for the clarification. I'll open future PRs as ready for review.