P1317R2 Remove Return Type Deduction In `apply()`

[StephanTLavavej]

WG21-P1317R2 Remove Return Type Deduction In apply()

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INCREASED feature-test macro (thanks @frederick-vs-ja):

#define __cpp_lib_apply 202506L

Note: We're focused on implementing the remaining library-only features in C++23. Until that's done, we will NOT be accepting PRs for C++26 features.

[frederick-vs-ja]

cplusplus/draft#7999 bumps FTM __cpp_lib_apply to 202506L.