Update phpstan/phpstan requirement from ^1.5 to ^1.5 || ^2.0

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-version: 2.1.54
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

composer.json

@@ -30,7 +30,7 @@
 	"require-dev" : {
 		"monolog/monolog" : "^1.0.0 || ^2.0.0",
 		"phpunit/phpunit" : ">=7.5", 
-		"phpstan/phpstan" : "^1.5"
+		"phpstan/phpstan" : "^1.5 || ^2.0"
 	},
 	"autoload" : {
 		"files": ["source/CAS.php"],