RFR: 8351419: java.net.http: Cleanup links in HttpResponse and module-info API doc comments

[Daniel Fuchs]

This is a trivial doc cleanup. HttpResponse and module-info have a few links that should use {@linkplain } instead of {@link } or <href>. Also I noticed one link target mismatch, and some clarification missing in the send/receive buffer properties.

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Commit messages:
 - 8351419

Changes: https://git.openjdk.org/jdk/pull/23945/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23945&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351419
  Stats: 14 lines in 2 files changed: 1 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/23945.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23945/head:pull/23945

PR: https://git.openjdk.org/jdk/pull/23945