Update graphql-server-core requirement from <2,>=1.2 to >=1.2,<3

Updates the requirements on [graphql-server-core](https://github.com/graphql-python/graphql-server-core) to permit the latest version.
- [Release notes](https://github.com/graphql-python/graphql-server-core/releases)
- [Commits](graphql-python/graphql-server@v1.2.0...v2.0.0)

---
updated-dependencies:
- dependency-name: graphql-server-core
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

setup.py

@@ -133,7 +133,7 @@ def run(self):
             "sphinxext.opengraph",
         ],
         "full": ["responder[graphql,openapi]"],
-        "graphql": ["graphene<3", "graphql-server-core>=1.2,<2"],
+        "graphql": ["graphene<3", "graphql-server-core>=1.2,<3"],
         "openapi": ["apispec>=1.0.0"],
         "release": ["build", "twine"],
         "test": ["flask", "mypy", "pytest", "pytest-cov", "pytest-mock"],