[tests] remove useless anonymous typedef

tests/value/enum.i

@@ -2,7 +2,7 @@
   
   STDOPT: #"-main f"
 */
-typedef enum counter {ZERO,ONE,TWO,LAST=TWO};
+enum counter {ZERO,ONE,TWO,LAST=TWO};
 
 int t [LAST + 1] = { 1 };
 int u [TWO + 1] = { 2 };

tests/value/oracle/enum.res.oracle

 [kernel] Parsing enum.i (no preprocessing)
-[kernel:parser:unnamed-typedef] enum.i:5: Warning: typedef without a name
 [eva] Analyzing a complete application starting at f
 [eva] Computing initial state
 [eva] Initial state computed