Fix stale Cloud Connector service catalog

What does this MR do and why?

This MR fixes that CloudConnector::AvailableServices.find_by_name can't find a service entry even if it's defined in access_data.yml, due to the caching with default expiry period, which is 8 hours. This effectively means a new service is not available during the period.

I realized this issue during the feature flag rollout:

ee/lib/gitlab/llm/vertex_ai/configuration.rb:37:in `access_token', ee/lib/gitlab/llm/vertex_ai/configuration.rb:47
...

undefined method `access_token' for nil:NilClass

            return ::CloudConnector::AvailableServices.find_by_name(:ai_gateway_proxy).access_token(user)
                                                                                      ^^^^^^^^^^^^^

source

Changelog: fixed

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