Fix ucxx versioning

[AyodeAwe]

This PR addresses the versioning discrepancy in the documentation of the ucxx library. Previously, we used the RAPIDS versioning convention for ucxx in our docs workflow and overwrote the RAPIDS versioning with ucxx's actual versioning during the deploy step. This PR updates the workflow to use the correct ucxx version number directly in our docs deployment workflow.

Before this PR is merged, this PR should be merged - the PR updates the build step in build_docs.sh to use the correct version numbers when uploading docs to s3.

Before both these PRs are merged, we should rename/re-sync the relevant directories up in s3 from the RAPIDS versioning used to ucxx's.

Testing: Changes in download_from_s3.sh were tested by running the download_lib_docs function locally. Other processing scripts were tested locally by downloading rmm and libucxx (legacy, stable, nightly) docs and running ci/post_process.sh. Outputs were as expected.

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[ajschmidt8]

After both these PRs are merged, we should rename/re-sync the relevant directories up in s3 from the RAPIDS versioning used to ucxx's.

The directories should be renamed before this PR is merged. Otherwise the build on the default branch will not complete successfully since the old docs are still named incorrectly