RFR: 8325361: Make sun.net.www.MessageHeader final

[Daniel Fuchs]

On Thu, 29 Feb 2024 12:16:38 GMT, Korov <duke at openjdk.org> wrote:

> Make sun.net.www.MessageHeader final, and remove `@SuppressWarnings("this-escape")`

The test results came back green. So please integrate!

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Marked as reviewed by dfuchs (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18060#pullrequestreview-1909584781