remove bad advice to use .attr() method

fix jquery#199

page/using-jquery-core/faq/how-do-i-check-uncheck-a-checkbox-input-or-radio-button.md

@@ -3,24 +3,12 @@ title:        How do I check/uncheck a checkbox input or radio button?
 source:       http://docs.jquery.com/Frequently_Asked_Questions
 ---
 
-There are two ways to check/uncheck a checkbox/radio button.
-
-Set the 'checked' attribute to true or false.
-
-```
-// Check #x
-$("#x").attr( "checked", true );
-
-// Uncheck #x
-$("#x").attr( "checked", false );
-```
-
-Add or remove the 'checked' attribute:
+You can check or uncheck a checkbox element or a radio button using the `.prop()` method:
 
 ```
 // Check #x
-$("#x").attr( "checked", "checked" );
+$("#x").prop( "checked", true );
 
 // Uncheck #x
-$("#x").removeAttr("checked");
+$("#x").prop( "checked", false );
 ```

page/using-jquery-core/faq/how-do-i-disable-enable-a-form-element.md

@@ -3,24 +3,12 @@ title:        How do I disable/enable a form element?
 source:       http://docs.jquery.com/Frequently_Asked_Questions
 ---
 
-There are two ways to disable/enable form elements.
-
-Set the 'disabled' attribute to true or false:
-
-```
-// Disable #x
-$("#x").attr( "disabled", true );
-
-// Enable #x
-$("#x").attr( "disabled", false );
-```
-
-Add or remove the 'disabled' attribute:
+You can enable or disable a form element using the `.prop()` method:
 
 ```
 // Disable #x
-$("#x").attr( "disabled", "disabled" );
+$("#x").prop( "disabled", true );
 
 // Enable #x
-$("#x").removeAttr("disabled");
+$("#x").prop( "disabled", false );
 ```