Fix build against libstdc++ shipped with GCC 16, which no longer
exposes the internal symbol std::__throw_bad_alloc() through <new>.

Backports the user-visible part of jemalloc upstream commit 1a15fe33
("Replace std::__throw_bad_alloc call with standard C++"), restricted
to the call site itself.  jemalloc's upstream patch also adds a
configure-time check that conditionally compiles either
'throw std::bad_alloc()' or 'std::terminate()' depending on whether
C++ exceptions are enabled, but ProxySQL always builds with C++
exceptions, so the simpler unconditional form is sufficient.

Refs:
  https://github.com/sysown/proxysql/issues/5770
  https://github.com/jemalloc/jemalloc/commit/1a15fe33a48c52bfe26ea83e49f0d317a47da3ea

--- src/jemalloc_cpp.cpp.orig
+++ src/jemalloc_cpp.cpp
@@ -67,7 +67,7 @@
 	}

 	if (ptr == nullptr && !nothrow)
-		std::__throw_bad_alloc();
+		throw std::bad_alloc();
 	return ptr;
 }