replaced tabs with spaces in docs.

docs/guide/model.md

@@ -258,7 +258,7 @@ for example the [[yii\validators\InlineValidator::$skipOnEmpty|skipOnEmpty]] pro
 [['birthdate'], 'validateAge', 'params' => ['min' => '12'], 'skipOnEmpty' => false],
 ```
 
-### conditional validation
+### Conditional validation
 
 To validate attributes only when certain conditions apply, e.g. the validation of
 one field depends on the value of another field you can use [[yii\validators\Validator::when|the `when` property]]
@@ -353,7 +353,7 @@ class User extends ActiveRecord
 }
 ```
 
-For the code above mass assignment will be allowed stsrictly according to `scenarios()`:
+For the code above mass assignment will be allowed strictly according to `scenarios()`:
 
 ```php
 $user = User::find(42);