Update php-http/curl-client requirement from ^1.7 to ^1.7 || ^2.0 (#3)

Updates the requirements on [php-http/curl-client](https://github.com/php-http/curl-client) to permit the latest version.
- [Release notes](https://github.com/php-http/curl-client/releases)
- [Changelog](https://github.com/php-http/curl-client/blob/master/CHANGELOG.md)
- [Commits](php-http/curl-client@v1.7.0...2.0.0)

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

composer.json

@@ -20,7 +20,7 @@
     },
     "require-dev": {
         "geocoder-php/provider-integration-tests": "^1.0",
-        "php-http/curl-client": "^1.7",
+        "php-http/curl-client": "^1.7 || ^2.0",
         "php-http/message": "^1.0",
         "phpunit/phpunit": "^6.5 || ^7.5"
     },