LibWasm: Fix Negate::name() to return "neg"

Negate was incorrectly returning "== 0", a copy/paste from EqualsZero.
This patch corrects it to return "neg", matching the operator's actual
semantics and WebAssembly mnemonics (f32.neg, f64.neg).

(cherry picked from commit 5f4ad17f89a5c58768251d079321412e97823bfe)

Userland/Libraries/LibWasm/AbstractMachine/Operators.h

@@ -547,7 +547,7 @@ struct Negate {
         return -lhs;
     }
 
-    static StringView name() { return "== 0"sv; }
+    static StringView name() { return "neg"sv; }
 };
 
 struct Ceil {