LibX86: Don't use "if (foo) [[unlikely]] { }" for now (to please clang)

Userland/Libraries/LibX86/Instruction.h

@@ -833,7 +833,7 @@ ALWAYS_INLINE Instruction::Instruction(InstructionStreamType& stream, bool o32,
             m_descriptor = &m_descriptor->slashes[rm() & 7];
     }
 
-    if (!m_descriptor->mnemonic) [[unlikely]] {
+    if (!m_descriptor->mnemonic) {
         if (has_sub_op()) {
             if (has_slash)
                 fprintf(stderr, "Instruction %02X %02X /%u not understood\n", m_op, m_sub_op, slash());