RFR: 8347348: Clarify that the HTTP server in jdk.httpserver module is not a full featured server

[Jaikiran Pai]

Can I please get a review of this doc-only change which clarifies the purpose of the HTTP server that's provided in the JDK's `jdk.httpserver` module? This should help avoid any confusion on the purpose of the server.

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Commit messages:
 - 8347348: Clarify that the HTTP server in jdk.httpserver module is not a full featured server

Changes: https://git.openjdk.org/jdk/pull/23004/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23004&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347348
  Stats: 7 lines in 1 file changed: 6 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23004.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23004/head:pull/23004

PR: https://git.openjdk.org/jdk/pull/23004