Update Scrutinizer to use PHP 8.0

Update Scrutinizer CI environment from PHP 7.4 to PHP 8.0 to match
the new minimum PHP version requirement.

This ensures code quality analysis runs on the correct PHP version.

Author: claude

.scrutinizer.yml

@@ -1,4 +1,4 @@
 build:
     environment:
-        php: 7.4
+        php: 8.0