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/Authentication/HMAC.h

@@ -7,12 +7,15 @@
 #pragma once
 
 #include <AK/ByteBuffer.h>
-#include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/StringView.h>
 #include <AK/Types.h>
 #include <AK/Vector.h>
 
+#ifndef KERNEL
+#    include <AK/String.h>
+#endif
+
 constexpr static auto IPAD = 0x36;
 constexpr static auto OPAD = 0x5c;
 
@@ -70,6 +73,7 @@ public:
         m_outer_hasher.update(m_key_data + m_inner_hasher.block_size(), m_outer_hasher.block_size());
     }
 
+#ifndef KERNEL
     String class_name() const
     {
         StringBuilder builder;
@@ -77,6 +81,7 @@ public:
         builder.append(m_inner_hasher.class_name());
         return builder.build();
     }
+#endif
 
 private:
     void derive_key(const u8* key, size_t length)