Update the minimum version of atdgen in clang-ocaml doc
Update the minimum version of atdgen in clang-ocaml doc

Summary: Forgot to change it

Test Plan: none

Reviewers: jul, mathieubaudet

Reviewed By: mathieubaudet

Subscribers: mathieubaudet

Differential Revision: https://phabricator.fb.com/D2245342

Signature: t1:2245342:1436988687:768c7ac5e4ba93ed03934988a26e9f285cd97d70

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