RFR: CODETOOLS-7903077: Remove @SuppressWarnings for --source 1.2 code

[Jonathan Gibbons]

Please review a trivial update to remove `@SuppressWarnings` annotations from `AppletWrapper`, which is still compiled with `--source 1.2` in the recommended build for `jtreg 6`.

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Commit messages:
 - CODETOOLS-7903077: Remove @SuppressWarnings for --source 1.2 code

Changes: https://git.openjdk.java.net/jtreg/pull/46/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=46&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903077
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/46.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/46/head:pull/46

PR: https://git.openjdk.java.net/jtreg/pull/46