Update "current release" to 23.1. Remove API diffs that are available from the release page.
Update "current release" to 23.1. Remove API diffs that are available from the release page.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=170739806

typetools/guava,mosoft521/guava,xasx/guava,EdwardLee03/guava,berndhopp/guava,Xaerxess/guava,mosoft521/guava,EdwardLee03/guava,xasx/guava,Xaerxess/guava,typetools/guava,rgoldberg/guava,rgoldberg/guava,google/guava,mosoft521/guava,google/guava,google/guava,berndhopp/guava