Update composer.json

Please update composer.json file to use newest **webmozart/assert**

```
    - Root composer.json requires league/openapi-psr7-validator ^0.22.0 -> satisfiable by league/openapi-psr7-validator[0.22].
    - league/openapi-psr7-validator 0.22 requires webmozart/assert ^1.4 -> found webmozart/assert[1.4.0, ..., 1.12.1] but it conflicts with your root composer.json require (^2.1).
```
