RFR: 8310999: Add @since info in jdk.jsobject files [v2]

[Roger Riggs]

> Source code cleanup.
> Add @since, remove unused imports and remove unnecessary SuppressWarnings of deprecation.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Remove unneeded @SuppressWarnings

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14775/files
  - new: https://git.openjdk.org/jdk/pull/14775/files/f63e9e9c..72333076

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14775&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14775&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14775.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14775/head:pull/14775

PR: https://git.openjdk.org/jdk/pull/14775