express-graphql >=0.10.0 instrumentation with node <10.4 doesn't work

The work in https://github.com/elastic/apm-agent-nodejs/pull/2511 to add support for more recent versions of `express-graphql` hit an issue: There is some issue with express-graphql `>=0.10.0` and node `<10.4` (released 2018-06-06) such that the wrapped `graphql.execute` called by express-graphql is not in the run context of the transaction, so the graphql span does not get created and the transaction does not get marked as a GraphQL transaction.

It works with express-graphql@0.9.0, FWIW. I'm not sure what is going on; but I'm also not sure it is worth supporting given node v10 is EOL at this point.