Updates GraphQL version to 1.2.0 for sub support

Author: Jay Herron

Package.resolved

@@ -7,7 +7,7 @@ let package = Package(
         .library(name: "GraphQLRxSwift", targets: ["GraphQLRxSwift"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/GraphQLSwift/GraphQL.git", .upToNextMajor(from: "1.1.7")),
+        .package(url: "https://github.com/GraphQLSwift/GraphQL.git", .upToNextMajor(from: "1.2.0")),
         .package(url: "https://github.com/GraphQLSwift/Graphiti.git", .upToNextMinor(from: "0.22.0")),
         .package(url: "https://github.com/ReactiveX/RxSwift.git", .upToNextMajor(from: "6.1.0"))
     ],