LibCrypto: Exclude class_name() methods from the Kernel

These are only used by Userland and contain infallible String
allocations, so let's just ifdef them out of the Kernel.

Userland/Libraries/LibCrypto/Hash/HashManager.h

@@ -191,12 +191,14 @@ public:
             [&](auto& hash) { hash.reset(); });
     }
 
+#ifndef KERNEL
     virtual String class_name() const override
     {
         return m_algorithm.visit(
             [&](const Empty&) -> String { return "UninitializedHashManager"; },
             [&](const auto& hash) { return hash.class_name(); });
     }
+#endif
 
     inline bool is(HashKind kind) const
     {