fix(tests): pin symfony/deprecation-contracts to ^2.5 in Drupal 9.5 fixture (#4049)

test_web_drupal_95 was crashing during Drupal's install script with a
fatal TypeError on PHP 7.4. The Drupal 9.5 composer.json has no lock
file, so `composer install --ignore-platform-reqs` resolves guzzlehttp/
guzzle to the latest 7.15.1, which pulls in symfony/deprecation-
contracts v3.7.1. That version's trigger_deprecation() signature uses
a `mixed ...$args` variadic typehint, which is only valid on PHP 8.0+
and is a fatal TypeError when the class is loaded/called on PHP 7.4.

--ignore-platform-reqs defeats platform.php's PHP version pin, so
composer happily selects a dependency graph that is incompatible with
the PHP version the job actually runs.

Pin symfony/deprecation-contracts to ^2.5 directly in the fixture's
require block so composer's solver is constrained to a version whose
API is compatible with PHP 7.4, regardless of what guzzle pulls in
transitively.

Author: Leiyks

tests/Frameworks/Drupal/Version_9_5/composer.json

@@ -12,7 +12,8 @@
         "composer/installers": "^1.9",
         "drupal/core": "self.version",
         "drupal/core-project-message": "self.version",
-        "drupal/core-vendor-hardening": "self.version"
+        "drupal/core-vendor-hardening": "self.version",
+        "symfony/deprecation-contracts": "^2.5"
     },
     "require-dev": {
         "behat/mink": "^1.8",