RFR: 8287099: Clean up terminology regarding doc comment descriptions.

[Pavel Rappo]

Use the term "main description".

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Commit messages:
 - Update copyright years
 - Initial commit

Changes: https://git.openjdk.java.net/jdk/pull/8818/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8818&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287099
  Stats: 11 lines in 6 files changed: 0 ins; 0 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8818.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8818/head:pull/8818

PR: https://git.openjdk.java.net/jdk/pull/8818