Remove outdated references to older Twig versions

doc/templates.rst

@@ -959,9 +959,6 @@ The following operators don't fit into any of the other categories:
       {{ user.('get' ~ name) }}
       {{ user?.(name) }}
 
-  Before Twig 3.15, use the :doc:`attribute <functions/attribute>` function
-  instead for the two previous use cases.
-
   Twig supports a specific syntax via the ``[]`` operator for accessing items
   on sequences and mappings:
 

src/Loader/FilesystemLoader.php

@@ -159,7 +159,6 @@ class FilesystemLoader implements LoaderInterface
 
     public function isFresh(string $name, int $time): bool
     {
-        // false support to be removed in 3.0
         if (null === $path = $this->findTemplate($name)) {
             return false;
         }