Bump guzzlehttp/oauth-subscriber from 0.6.0 to 0.9.4

Bumps [guzzlehttp/oauth-subscriber](https://github.com/guzzle/oauth-subscriber) from 0.6.0 to 0.9.4.
- [Release notes](https://github.com/guzzle/oauth-subscriber/releases)
- [Changelog](https://github.com/guzzle/oauth-subscriber/blob/0.9/CHANGELOG.md)
- [Commits](guzzle/oauth-subscriber@0.6.0...0.9.4)

---
updated-dependencies:
- dependency-name: guzzlehttp/oauth-subscriber
  dependency-version: 0.9.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

composer.json

@@ -20,7 +20,7 @@
     "ext-openssl": "*",
     "ext-pdo": "*",
     "guzzlehttp/guzzle": "^7.8.1",
-    "guzzlehttp/oauth-subscriber": "^0.6",
+    "guzzlehttp/oauth-subscriber": "^0.9",
     "michelf/php-markdown": "^2",
     "pimple/pimple": "^3.5",
     "psr/container": "^2.0.2",