docs: replace "Form validation" with "Validation"

Form validation is the name of CI3 library.

Author: kenjis

user_guide_src/source/concepts/security.rst

@@ -39,7 +39,7 @@ CodeIgniter provisions
 ======================
 
 - :doc:`HTTP library <../incoming/incomingrequest>` provides for input field filtering & content metadata
-- Form validation library
+- Validation library
 
 *********************************************
 A2 Weak authentication and session management
@@ -82,7 +82,7 @@ CodeIgniter provisions
 ======================
 
 - esc function
-- Form validation library
+- Validation library
 
 ***********************************
 A4 Insecure Direct Object Reference
@@ -103,7 +103,7 @@ OWASP recommendations
 CodeIgniter provisions
 ======================
 
-- Form validation library
+- Validation library
 - Easy to add third party authentication
 
 ****************************

user_guide_src/source/helpers/form_helper.rst

@@ -510,8 +510,8 @@ The following functions are available:
         <input type="radio" name="myradio" value="1" <?= set_radio('myradio', '1', true) ?> />
         <input type="radio" name="myradio" value="2" <?= set_radio('myradio', '2') ?> />
 
-    .. note:: If you are using the Form Validation class, you must always specify
+    .. note:: If you are using the Validation class, you must always specify
         a rule for your field, even if empty, in order for the ``set_*()``
-        functions to work. This is because if a Form Validation object is
+        functions to work. This is because if a Validation object is
         defined, the control for ``set_*()`` is handed over to a method of the
         class instead of the generic helper function.