[ci/build] Fix entrypoints test and pin outlines version

[khluu]

#10576 ran CI and passed with outlines==0.1.8 but outline 0.1.9 released and had a change to use outlines-core instead of outlines for one of the import paths: https://github.com/dottxt-ai/outlines/pull/1311/files#diff-b29e16a237d75d6560f08ec4c09049474c96d34e4c4f544dde27002ae1f684d9L3 which broke CI since outlines version is not pinned.

This PR fixes the import path and also pins outlines==0.1.9

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.
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