Remove version number from author section of the documentation

[philwebb]

I'm not sure if this is related to the new docs style sheet or something else, but we now have a version number in the authors list:

vs

[mbhave]

Depending on the fix, there might be some overlap with #20896.

[wilkinsona]

I don't think it's related to the new docs stylesheet as it's been that was since 2.3.0.M1. I believe it's happening because the Gradle Asciidoctor plugin configures the revnumber attribute by default.

When revnumber is set or inferred from the source document, it's included in the byline. In other words, we're seeing Asciidoctor's standard behaviour here. If we don't like it, we can get rid of it by explicitly setting the revnumber attribute to null.