Remove the unused variables after working on CS0077 (#43368)

Author: BartoszKlonowski

docs/csharp/misc/cs0077.md

@@ -21,11 +21,7 @@ However, using [pattern matching](../fundamentals/functional/pattern-matching.md
 ```csharp  
 // CS0077.cs  
 using System;  
-  
-class C  
-{  
-}  
-  
+
 struct S  
 {  
 }  
@@ -34,17 +30,15 @@ class M
 {  
    public static void Main()  
    {  
-      object o1, o2;  
-      C c;  
+      object o;
       S s;  
+
+      o = new S();
 
-      o1 = new C();  
-      o2 = new S();  
-  
-      s = o2 as S;    // CS0077, S is not a reference type
+      s = o as S;    // CS0077, S is not a reference type
 
       // Use pattern matching instead of as
-      if (o2 is S sValue)
+      if (o is S sValue)
       {
           s = sValue;
       }