Remove symfony/polyfill-php86 from require-dev (#3521)

The polyfill was masking the absence of SortDirection on Laravel < 13.8:
since it was installed in all CI runs (including laravel: 12.*), the
class always existed and bugs in code paths that depend on its absence
could not be detected.

On Laravel >= 13.8, the polyfill is available as a transitive dependency
so SortDirection-specific tests still run via the class_exists() guard.

Author: GromNaN

composer.json

@@ -63,8 +63,7 @@
         "phpstan/phpstan": "^1.10|^2.1",
         "phpunit/phpunit": "^10.3|^11.5.3|^12.5.12",
         "rector/rector": "^1.2|^2.3",
-        "spatie/laravel-query-builder": "^5.6|^6",
-        "symfony/polyfill-php86": "^1.37"
+        "spatie/laravel-query-builder": "^5.6|^6"
     },
     "conflict": {
         "illuminate/bus": "< 10.37.2"