[backport] [doc][R] Update link. (#8998)#9001

Merged

trivialfis merged 1 commit intodmlc:release_1.7.0from trivialfis:backport-8998

Mar 30, 2023

+4-4

Commits on Mar 30, 2023

[backport] [doc][R] Update link. (dmlc#8998 )
trivialfis
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