git: openjdk/jdk-sandbox: classfile-api-branch: fixed building docs

[Adam Sotona]

Changeset: b914fde0
Author:    Adam Sotona <asotona at openjdk.org>
Date:      2023-03-09 09:00:18 +0000
URL:       https://git.openjdk.org/jdk-sandbox/commit/b914fde01ef92ba5b51779aae2af21678c5df6bf

fixed building docs

! make/Docs.gmk