RFR: 8378118: Test tools/jimage/JImageBadFileTest.java failed on Windows

[David Beaumont]

Removed the manual file tidyup on the expectation that jtreg will sort that all out.
Switched to using Utils.createTempFile() while I was there.

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Commit messages:
 - Remove file cleanup and switch to Utils.createTempFile()

Changes: https://git.openjdk.org/jdk/pull/29783/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29783&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378118
  Stats: 46 lines in 1 file changed: 2 ins; 23 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/29783.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29783/head:pull/29783

PR: https://git.openjdk.org/jdk/pull/29783