git: openjdk/jdk-sandbox: jdk.javadoc/snippets: Update missed @since tag

[duke]

Changeset: d0bdbabf
Author:    pavelrappo <pavel.rappo at gmail.com>
Date:      2021-05-10 20:22:53 +0000
URL:       https://git.openjdk.java.net/jdk-sandbox/commit/d0bdbabf240a57fa4dd55fe40f1b1490cf25b6eb

Update missed @since tag

! src/jdk.compiler/share/classes/com/sun/source/util/DocTreeFactory.java