RFR: Replace fibers by virtual threads in the test summary

[Leonid Mesnik]

Replace fibers by virtual threads in the test summary

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Commit messages:
 - Change fibers to virtual threads

Changes: https://git.openjdk.java.net/loom/pull/6/files
 Webrev: https://webrevs.openjdk.java.net/loom/6/webrev.00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/loom/pull/6.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/6/head:pull/6

PR: https://git.openjdk.java.net/loom/pull/6