RFR: 7540: IItemCollectionJsonSerializerTest.java might fail on Windows due to line endings

[Christoph Langer]

Fix test IItemCollectionJsonSerializerTest.java

The line endings should be normalized, to avoid errors on Windows due to incompatible line ending formats.

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Commit messages:
 - JMC-7540

Changes: https://git.openjdk.java.net/jmc/pull/370/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=370&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7540
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jmc/pull/370.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/370/head:pull/370

PR: https://git.openjdk.java.net/jmc/pull/370