[Test - No need to review] chore: Test with custom endpoint

[lqiu96]

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Fixes #<issue_number_goes_here> ☕️

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[generated-files-bot]

Warning: This pull request is touching the following templated files:

• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/AdminServiceStubSettings.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/CursorServiceStubSettings.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/PartitionAssignmentServiceStubSettings.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/PublisherServiceStubSettings.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/SubscriberServiceStubSettings.java
• google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/v1/stub/TopicStatsServiceStubSettings.java