RFR: 8322078: ZipSourceCache.testKeySourceMapping() test fails with The process cannot access the file because it is being used by another process

[Sean Coffey]

trivial test edit to use FileUtils.deleteFileIfExistsWithRetry test library API

tested on CI system with test-repeat = 20 - no issues seen.

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Commit messages:
 - 8322078

Changes: https://git.openjdk.org/jdk/pull/17169/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17169&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322078
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17169.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17169/head:pull/17169

PR: https://git.openjdk.org/jdk/pull/17169