RFR: 8272334: com.sun.net.httpserver.HttpExchange: Improve API doc of getRequestHeaders [v2]

[Julia Boes]

> This is a doc-only fix that improves the wording of the API doc of `getRequestHeaders()`. The other changes are trivial cleanup.

Julia Boes has updated the pull request incrementally with one additional commit since the last revision:

  small fix of tense

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5100/files
  - new: https://git.openjdk.java.net/jdk/pull/5100/files/5fdccc32..9b87ced4

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5100&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5100&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5100.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5100/head:pull/5100

PR: https://git.openjdk.java.net/jdk/pull/5100