Update simplesamlphp/saml2-legacy requirement

Updates the requirements on [simplesamlphp/saml2-legacy](https://github.com/simplesamlphp/saml2-legacy) to permit the latest version.

Updates `simplesamlphp/saml2-legacy` to 4.19.0
- [Commits](simplesamlphp/saml2-legacy@v4.18.1...v4.19.0)

---
updated-dependencies:
- dependency-name: simplesamlphp/saml2-legacy
  dependency-version: 4.19.0
  dependency-type: direct:production
  dependency-group: production-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

composer.json

@@ -33,7 +33,7 @@
 
         "simplesamlphp/assert": "~1.8.1",
         "simplesamlphp/composer-module-installer": "~1.4.0",
-        "simplesamlphp/saml2-legacy": "~4.18.1",
+        "simplesamlphp/saml2-legacy": "~4.19.0",
         "simplesamlphp/simplesamlphp": "~2.4.0"
     },
     "require-dev": {