Bump up phpstan and psalm's version.

composer.json

@@ -112,7 +112,7 @@
             "@phpstan",
             "@psalm"
         ],
-        "stan-setup": "cp composer.json composer.backup && composer require --dev phpstan/phpstan:0.12.39 psalm/phar:~3.15 && mv composer.backup composer.json"
+        "stan-setup": "cp composer.json composer.backup && composer require --dev phpstan/phpstan:0.12.48 psalm/phar:~3.16 && mv composer.backup composer.json"
     },
     "config": {
         "sort-packages": true,

phpstan-baseline.neon

@@ -326,11 +326,6 @@ parameters:
 			path: src/Http/Session.php
 
 		-
-			message: "#^Variable \\$_SESSION in isset\\(\\) always exists and is not nullable\\.$#"
-			count: 2
-			path: src/Http/Session.php
-
-		-
 			message: "#^Call to an undefined method Cake\\\\Chronos\\\\DifferenceFormatterInterface\\:\\:dateAgoInWords\\(\\)\\.$#"
 			count: 1
 			path: src/I18n/Date.php