Increase validation timeout for GitlabSchema in dump rake task

What does this MR do and why?

Increase validation timeout for GitlabSchema in dump rake task

Previously, running rake gitlab:graphql:schema:dump would cause the inspection query to timeout which broke CI job graphql-verify.

The rake task gitlab:graphql:validate already increased the timeout the account for slow CI runners.

This commit increases the validation timeout also for the dump rake task to valid flaky CI pipelines.

See gitlab-org/quality/engineering-productivity/master-broken-incidents#5902 (closed)

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How to set up and validate locally

bundle exec rake gitlab:graphql:schema:dump
bundle exec rake gitlab:graphql:validate