Incompatibility with guzzlehttp/psr7 ^2.0 - Call to undefined function parse_query()


The hubspot-api-php library is incompatible with the latest versions of `guzzlehttp/psr7` (^2.0+). When using `guzzlehttp/guzzle` ^7.10 (which requires `guzzlehttp/psr7` ^2.0), the following error occurs:


```
In Conversion.php line 73:
                                                            
  Call to undefined function GuzzleHttp\Psr7\parse_query()  
```