Use strict comparison

The new code should be used as soon as 2.8.0 is available

Author: Grégoire Paris

setup/bundles.rst

@@ -173,7 +173,7 @@ Before diving into the specifics of the most common edge cases, the general
 recommendation is to **not rely on the Symfony Kernel version** to decide which
 code to use::
 
-    if (Kernel::VERSION_ID <= 20800) {
+    if (Kernel::VERSION_ID < 20800) {
         // code for Symfony 2.x
     } else {
         // code for Symfony 3.x