ext/json: Remove `zend_never_inline` qualifier for `php_json_is_valid_double()`

[Girgias]

Description

It seems the MSVC bug has been resolved:

• https://developercommunity.visualstudio.com/t/corrupt-optimization-on-arm64-with-Ox-/10102551
• https://developercommunity.visualstudio.com/t/Prev-Issue---with-__assume-isnan-/1597317
  So should we remove the ifdef?

@cmb69 you know more about Windows than I do, so is this proposal reasonable?

[cmb69]

Hmm, unsure. The first bug report was about ARM64 (and the preprocessor conditional is too), but that ticket has been closed as duplicate of the second report which is not particularly about ARM64. Now that second ticket claims the issue had been fixed in VS 17.3, which is available for more than 2 years. Assuming that the issue had been fixed for ARM64 back then as well, removing the conditinal makes sense to me. Unfortunately, there are still no public GH runners for ARM64 on Windows available, so I wouldn't be able to double-check.