git: openjdk/loom: fibers: More tests, tweak javadoc

[duke]

Changeset: 3bfc89aa
Author:    Alan Bateman <alan.bateman at oracle.com>
Date:      2023-04-26 11:42:34 +0000
URL:       https://git.openjdk.org/loom/commit/3bfc89aa5bd133870e021a74904a760bf2ecff4a

More tests, tweak javadoc

! src/java.base/share/classes/java/util/concurrent/StructuredTaskScope.java
! test/jdk/java/util/concurrent/StructuredTaskScope/StructuredTaskScopeTest.java