Typo in Flask view context

Hi all, just a small one:

The line https://github.com/graphql-python/graphql-server/blob/2d5ac9539307d6db22b3364a61063e050c3f20b9/src/graphql_server/flask/views.py#L145 creates the context with `operationName` but the template https://github.com/graphql-python/graphql-server/blob/2d5ac9539307d6db22b3364a61063e050c3f20b9/src/graphql_server/static/graphiql.html#L199 expects `operation_name`. Probably `request_data.to_template_context()` is meant to be used which does use `operation_name`: https://github.com/graphql-python/graphql-server/blob/2d5ac9539307d6db22b3364a61063e050c3f20b9/src/graphql_server/http/__init__.py#L74

Thanks!