RFR: Fixed links and a few other minor changes

[Alexey Ivanov]

On Tue, 21 Jun 2022 14:45:37 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

> Changed openjdk.java.net to openjdk.org.

src/guide/about-this-guide.md line 5:

> 3: This guide is being maintained through the [OpenJDK Developers' Guide Project](https://openjdk.org/census#guide). The [source repository](https://urldefense.com/v3/__https://github.com/openjdk/guide__;!!ACWV5N9M2RV99hQ!KMxBUdAIb6ISTvF2ooqBr3vmzGClDPnRgfPxUa-FZn4h_yP5dlDKJeyWWY811cLJtFlwtGTH6Ox07agQeGHUzw$ ) is available at GitHub. The revision hash at the bottom of this page refers to the last published commit.
> 4: 
> 5: Comments and questions may be sent to [guide-dev (at) openjdk.org](mailto:guide-dev-at-openjdk.org). Please let us know if there's anything in the guide that isn't clear.

Should the email address be a link? If you click it, you'll be unable to send the email until you edit the address and replace `-at-` with `@`.

The email addresses in the `code-owners.md` file are the real ones. Does it make sense to update this one to be the correct email address of the mailing list?

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PR: https://git.openjdk.org/guide/pull/89