Fix #41439: Update the documentation with the correct information. (#69377)

Fixes #41439

The documentation is update to say it is allowed to have omitted
parameter names if the variable is not used

Author: da-viper

clang-tools-extra/docs/clang-tidy/checks/readability/named-parameter.rst

@@ -10,7 +10,16 @@ Guide:
 
 https://google.github.io/styleguide/cppguide.html#Function_Declarations_and_Definitions
 
-All parameters should be named, with identical names in the declaration and
-implementation.
+All parameters should have the same name in both the function declaration and definition.
+If a parameter is not utilized, its name can be commented out in a function definition.
+
+.. code-block:: c++
+
+    int doingSomething(int a, int b, int c);
+
+    int doingSomething(int a, int b, int /*c*/) {
+        // Ok: the third param is not used
+        return a + b;
+    }
 
 Corresponding cpplint.py check name: `readability/function`.