RFR: JDK-8292330: Update JCov version to 3.0.13

[Alexandre Iline]

Switch to a new JCov version

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Commit messages:
 - JDK-8292330: Update JCov version to 3.0.13

Changes: https://git.openjdk.org/jdk/pull/10581/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10581&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292330
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10581.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10581/head:pull/10581

PR: https://git.openjdk.org/jdk/pull/10581