graphql: Add Enum.values and EnumValue#value method signatures

[aruma256]

Add Enum.values and EnumValue#value to the graphql gem RBS type definitions.

• https://github.com/rmosolgo/graphql-ruby/blob/v1.12.0/lib/graphql/schema/enum.rb#L47-L52
• https://github.com/rmosolgo/graphql-ruby/blob/v1.12.0/lib/graphql/schema/enum_value.rb#L69-L74

[github-actions]

@aruma256 Thanks for your contribution!

Please follow the instructions below for each change.
See also: https://github.com/ruby/gem_rbs_collection/blob/main/docs/CONTRIBUTING.md

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graphql

You changed RBS files for an existing gem.
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[aruma256]

/merge