[OpenApi] Use GetCustomAttributes<T>

Use `GetCustomAttributes<T>()` instead of `GetCustomAttributes().OfType<ValidationAttribute>()` to avoid need to use LINQ.

Author: martincostello

src/OpenApi/src/Extensions/JsonNodeSchemaExtensions.cs

@@ -320,7 +320,7 @@ internal static void ApplyParameterInfo(this JsonNode schema, ApiParameterDescri
                 schema.ApplyDefaultValue(defaultValueAttribute.Value, jsonTypeInfo);
             }
 
-            if (parameterInfo.GetCustomAttributes().OfType<ValidationAttribute>() is { } validationAttributes)
+            if (parameterInfo.GetCustomAttributes<ValidationAttribute>() is { } validationAttributes)
             {
                 schema.ApplyValidationAttributes(validationAttributes);
             }