Remove unused macro

The V8_HAS_DECLSPEC_NORETURN macro is unused since
https://crrev.com/c/529072, where we switched to the standard
[[noreturn]] attribute.

R=ulan@chromium.org

Bug: v8:9810
Change-Id: Ifd76c967df1da7bb71369e61cd0adc1807b62d44
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1847365Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64175}

include/v8config.h

@@ -251,7 +251,6 @@
 //                                        supported
 //  V8_HAS_DECLSPEC_NOINLINE            - __declspec(noinline) supported
 //  V8_HAS_DECLSPEC_SELECTANY           - __declspec(selectany) supported
-//  V8_HAS_DECLSPEC_NORETURN            - __declspec(noreturn) supported
 //  V8_HAS___FORCEINLINE                - __forceinline supported
 //
 // Note that testing for compilers and/or features must be done using #if
@@ -336,7 +335,6 @@
 
 # define V8_HAS_DECLSPEC_NOINLINE 1
 # define V8_HAS_DECLSPEC_SELECTANY 1
-# define V8_HAS_DECLSPEC_NORETURN 1
 
 # define V8_HAS___FORCEINLINE 1