Update simplesamlphp/simplesamlphp-test-framework requirement (#61)

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

Updates `simplesamlphp/simplesamlphp-test-framework` to 1.9.1
- [Commits](simplesamlphp/simplesamlphp-test-framework@v1.8.0...v1.9.1)

---
updated-dependencies:
- dependency-name: simplesamlphp/simplesamlphp-test-framework
  dependency-version: 1.9.1
  dependency-type: direct:development
  dependency-group: dev-dependencies
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

composer.json

@@ -47,7 +47,7 @@
         "simplesamlphp/xml-common": "~1.24.0"
     },
     "require-dev": {
-        "simplesamlphp/simplesamlphp-test-framework": "~1.8.0"
+        "simplesamlphp/simplesamlphp-test-framework": "~1.9.1"
     },
     "config": {
         "allow-plugins": {