Add Ruby 3.4 to CI

Author: DmitryTsepelev

.github/workflows/rspec.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [3.1, 3.2, 3.3]
+        ruby: [3.1, 3.2, 3.3, 3.4]
         gemfile: [
           "gemfiles/graphql_2_1_4.gemfile",
           "gemfiles/graphql_2_3_0.gemfile",