minor #10895 Update micro_kernel_trait.rst (guillaumesmo)

This PR was merged into the 4.1 branch.

Discussion
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Update micro_kernel_trait.rst

Fixes #10858

this was previously (in 4.0) kernel:randomNumber, it was changed to Kernel::randomNumber but that doesn't work

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Commits
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337c59c Update micro_kernel_trait.rst

configuration/micro_kernel_trait.rst

@@ -55,7 +55,7 @@ Next, create an ``index.php`` file that defines the kernel class and executes it
         {
             // kernel is a service that points to this class
             // optional 3rd argument is the route name
-            $routes->add('/random/{limit}', 'Kernel::randomNumber');
+            $routes->add('/random/{limit}', 'kernel::randomNumber');
         }
 
         public function randomNumber($limit)