[libc++] Remove emscripten handling from exception_fallback.ipp

Emscripten doesn't use this file (at least not anymore), it uses
exception_libcxxabi.ipp since _LIBCPPABI_VERSION is defined.

Differential Revision: https://reviews.llvm.org/D91041

libcxx/src/support/runtime/exception_fallback.ipp

@@ -49,7 +49,6 @@ get_terminate() _NOEXCEPT
   return __libcpp_atomic_load(&__terminate_handler);
 }
 
-#ifndef __EMSCRIPTEN__ // We provide this in JS
 _LIBCPP_NORETURN
 void
 terminate() _NOEXCEPT
@@ -72,9 +71,7 @@ terminate() _NOEXCEPT
     }
 #endif  // _LIBCPP_NO_EXCEPTIONS
 }
-#endif // !__EMSCRIPTEN__
 
-#if !defined(__EMSCRIPTEN__)
 bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
 
 int uncaught_exceptions() _NOEXCEPT
@@ -83,7 +80,6 @@ int uncaught_exceptions() _NOEXCEPT
   fprintf(stderr, "uncaught_exceptions not yet implemented\n");
   ::abort();
 }
-#endif // !__EMSCRIPTEN__
 
 
 exception::~exception() _NOEXCEPT