Update tests.yml

Author: staabm

.github/workflows/tests.yml

@@ -55,7 +55,7 @@ jobs:
         shell: bash
         run: |
           composer require --dev phpunit/phpunit:^12 brianium/paratest:^7.16 symfony/process:^7 symfony/string:^7 symfony/console:^7 --update-with-dependencies --ignore-platform-reqs --working-dir=tests
-          composer require --dev phpunit/phpunit:^12 sebastian/diff --update-with-dependencies --ignore-platform-reqs
+          composer require --dev phpunit/phpunit:^12 sebastian/diff:^6 --update-with-dependencies --ignore-platform-reqs
 
       - name: "Check PHP configuration"
         run: "vendor/bin/phpunit --check-php-configuration"
@@ -275,7 +275,7 @@ jobs:
         shell: bash
         run: |
           composer require --dev phpunit/phpunit:^12 brianium/paratest:^7.16 symfony/process:^7 symfony/string:^7 symfony/console:^7 --update-with-dependencies --ignore-platform-reqs --working-dir=tests
-          composer require --dev phpunit/phpunit:^12 sebastian/diff --update-with-dependencies --ignore-platform-reqs
+          composer require --dev phpunit/phpunit:^12 sebastian/diff:^6 --update-with-dependencies --ignore-platform-reqs
 
       - uses: "ramsey/composer-install@v3"
         with: