[jdk11u-dev] RFR: 8236505: Mark jdk/editpad/EditPadTest.java as @headful

[Goetz Lindenmaier]

I backport this for parity with 11.0.15-oracle.

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Commit messages:
 - Backport 7acec3f161234b99da76193781296157b98d689c

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/789/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=789&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8236505
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/789.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/789/head:pull/789

PR: https://git.openjdk.java.net/jdk11u-dev/pull/789