fix pagable method name. (Azure#51671)

Author: haiyuazhang

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/src/Providers/OperationMethodProviders/PageableOperationMethodProvider.cs

@@ -70,7 +70,7 @@ protected MethodSignature CreateSignature()
                 : new CSharpType(typeof(Pageable<>), actualItemType);
             var methodName = _methodKind == ResourceOperationKind.List
                 ? (_isAsync ? "GetAllAsync" : "GetAll")
-                : (_isAsync ? $"{_convenienceMethod.Signature.Name}Async" : _convenienceMethod.Signature.Name);
+                : _convenienceMethod.Signature.Name;
 
             return new MethodSignature(
                 methodName,