Update jetbrains/phpstorm-stubs requirement from ^2019.3 to ^2026.2

Updates the requirements on [jetbrains/phpstorm-stubs](https://github.com/JetBrains/phpstorm-stubs) to permit the latest version.
- [Release notes](https://github.com/JetBrains/phpstorm-stubs/releases)
- [Commits](JetBrains/phpstorm-stubs@v2019.3...v2026.2)

---
updated-dependencies:
- dependency-name: jetbrains/phpstorm-stubs
  dependency-version: '2026.2'
  dependency-type: direct:development
...

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

Author: dependabot[bot]

composer.json

@@ -35,7 +35,7 @@
     "require-dev": {
         "ext-json": "*",
         "phpunit/phpunit": "^9",
-        "jetbrains/phpstorm-stubs": "^2019.3",
+        "jetbrains/phpstorm-stubs": "^2026.2",
         "psalm/phar": "6.16.*"
     },
     "autoload": {