minor #5102 Removed duplicate "long"s in length constraint (ByStones)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #5102).

Discussion
----------

Removed duplicate "long"s in length constraint

| Q             | A
| ------------- | ---
| Doc fix?      | [yes]
| New docs?     | [no]
| Applies to    | 2.5+

The maxMessage seems to have one long too many. This does apply to all maintained versions.

Alternative could be:
```
maxMessage: "Your first name cannot be more than {{ limit }} characters long"
```

Commits
-------

dcffc02 Removed duplicate "long"s

reference/constraints/Length.rst

@@ -36,7 +36,7 @@ To verify that the ``firstName`` field length of a class is between "2" and
                         min: 2
                         max: 50
                         minMessage: "Your first name must be at least {{ limit }} characters long"
-                        maxMessage: "Your first name cannot be longer than {{ limit }} characters long"
+                        maxMessage: "Your first name cannot be longer than {{ limit }} characters"
 
     .. code-block:: php-annotations
 
@@ -52,7 +52,7 @@ To verify that the ``firstName`` field length of a class is between "2" and
              *      min = 2,
              *      max = 50,
              *      minMessage = "Your first name must be at least {{ limit }} characters long",
-             *      maxMessage = "Your first name cannot be longer than {{ limit }} characters long"
+             *      maxMessage = "Your first name cannot be longer than {{ limit }} characters"
              * )
              */
              protected $firstName;
@@ -72,7 +72,7 @@ To verify that the ``firstName`` field length of a class is between "2" and
                         <option name="min">2</option>
                         <option name="max">50</option>
                         <option name="minMessage">Your first name must be at least {{ limit }} characters long</option>
-                        <option name="maxMessage">Your first name cannot be longer than {{ limit }} characters long</option>
+                        <option name="maxMessage">Your first name cannot be longer than {{ limit }} characters</option>
                     </constraint>
                 </property>
             </class>
@@ -94,7 +94,7 @@ To verify that the ``firstName`` field length of a class is between "2" and
                     'min'        => 2,
                     'max'        => 50,
                     'minMessage' => 'Your first name must be at least {{ limit }} characters long',
-                    'maxMessage' => 'Your first name cannot be longer than {{ limit }} characters long',
+                    'maxMessage' => 'Your first name cannot be longer than {{ limit }} characters',
                 )));
             }
         }