Kernel: Fix a dmesgln() format error

Author: https://github.com/alimpfard
Commit: 531d72fdfd
Pull-request: https://github.com/SerenityOS/serenity/pull/5468

Kernel/Heap/kmalloc.cpp

@@ -248,7 +248,7 @@ void* kmalloc_impl(size_t size)
 
     void* ptr = g_kmalloc_global->m_heap.allocate(size);
     if (!ptr) {
-        PANIC("kmalloc: Out of memory (requested size: {})");
+        PANIC("kmalloc: Out of memory (requested size: {})", size);
     }
 
     return ptr;