Update Symfony version constraints

Pin them to the 6.4 version we built this app on

composer.json

@@ -26,18 +26,18 @@
         "surfnet/stepup-bundle": "^6.0",
         "surfnet/stepup-middleware-client-bundle": "^5.0.0",
         "surfnet/stepup-saml-bundle": "^6.0",
-        "symfony/asset": "^6.0",
-        "symfony/expression-language": "^6.0",
+        "symfony/asset": "6.4.*",
+        "symfony/expression-language": "6.4.*",
         "symfony/flex": "^v2.4.3",
-        "symfony/form": "^6.0",
+        "symfony/form": "6.4.*",
         "symfony/framework-bundle": "6.4.*",
-        "symfony/http-foundation": "^6.0",
+        "symfony/http-foundation": "6.4.*",
         "symfony/monolog-bundle": "^3.5",
         "symfony/runtime": "6.4.*",
-        "symfony/security-bundle": "^6.0",
-        "symfony/translation": "^6.0",
-        "symfony/twig-bundle": "^6.0",
-        "symfony/validator": "^6.0",
+        "symfony/security-bundle": "6.4.*",
+        "symfony/translation": "6.4.*",
+        "symfony/twig-bundle": "6.4.*",
+        "symfony/validator": "6.4.*",
         "symfony/webpack-encore-bundle": "^1.7",
         "twbs/bootstrap": "~3.3.0",
         "twig/extra-bundle": "^3.0",
@@ -56,9 +56,9 @@
         "slevomat/coding-standard": "^8.13",
         "squizlabs/php_codesniffer": "^3.4",
         "symfony/maker-bundle": "^1.19",
-        "symfony/phpunit-bridge": "^6.0",
+        "symfony/phpunit-bridge": "6.4.*",
         "symfony/stopwatch": "^5.1",
-        "symfony/web-profiler-bundle": "^6.0"
+        "symfony/web-profiler-bundle": "6.4.*"
     },
     "conflict": {
         "symfony/symfony": "*"