[libc++/abi] Replace uses of _NOEXCEPT in src/ by noexcept

We always build the libraries in a Standard mode that supports noexcept,
so there's no need to use the _NOEXCEPT macro.

Differential Revision: https://reviews.llvm.org/D97700

GitOrigin-RevId: 5601305fb30bf585c397e62d2d3a8a712e47d70b
diff --git a/src/condition_variable.cpp b/src/condition_variable.cpp
index d133b01..1e29083 100644
--- a/src/condition_variable.cpp
+++ b/src/condition_variable.cpp
@@ -24,19 +24,19 @@
 // ~condition_variable is defined elsewhere.
 
 void
-condition_variable::notify_one() _NOEXCEPT
+condition_variable::notify_one() noexcept
 {
     __libcpp_condvar_signal(&__cv_);
 }
 
 void
-condition_variable::notify_all() _NOEXCEPT
+condition_variable::notify_all() noexcept
 {
     __libcpp_condvar_broadcast(&__cv_);
 }
 
 void
-condition_variable::wait(unique_lock<mutex>& lk) _NOEXCEPT
+condition_variable::wait(unique_lock<mutex>& lk) noexcept
 {
     if (!lk.owns_lock())
         __throw_system_error(EPERM,
@@ -48,7 +48,7 @@
 
 void
 condition_variable::__do_timed_wait(unique_lock<mutex>& lk,
-     chrono::time_point<chrono::system_clock, chrono::nanoseconds> tp) _NOEXCEPT
+     chrono::time_point<chrono::system_clock, chrono::nanoseconds> tp) noexcept
 {
     using namespace chrono;
     if (!lk.owns_lock())