graphql: Fix icinga check string for graphql instance
graphql: Fix icinga check string for graphql instance

Default graphql configuration will looks up for the basic 'graphql', one must look for
'GraphQL' instead for the check to go green.

SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-site