test: fix dependency of latest graphql release on fiber-storage gem

Signed-off-by: Arjun Rajappa <arjun.rajappa@ibm.com>

Author: arjun-rajappa

gemfiles/graphql_20.gemfile

@@ -11,5 +11,6 @@ gem "puma"
 gem "rack-test"
 gem "simplecov", "~> 0.21.2"
 gem "graphql", ">= 2.0.21", "< 3.0"
+gem "fiber-storage"
 
 gemspec path: "../"