RFR: 8328553: Get rid of JApplet in test/jdk/sanity/client/lib/SwingSet2/src/DemoModule.java

[lawrence.andrews]

1) Replaced JApplet with JPanel 
2) Tests passed before and after fix

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Commit messages:
 - Left a blank line at the end of the file
 - 8328553: Get rid of JApplet in test/jdk/sanity/client/lib/SwingSet2/src/DemoModule.java

Changes: https://git.openjdk.org/jdk/pull/20450/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20450&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328553
  Stats: 11 lines in 1 file changed: 1 ins; 7 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/20450.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20450/head:pull/20450

PR: https://git.openjdk.org/jdk/pull/20450