RFR: 8259487: Remove unused StarTask

[Kim Barrett]

Please review this change which removes the StarTask class.  It was
superseded by ScannerTask in JDK-8244684 and JDK-8245022, and is no longer
used.

Testing:
mach5 tier1

-------------

Commit messages:
 - remove StarTask

Changes: https://git.openjdk.java.net/jdk/pull/2277/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2277&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259487
  Stats: 31 lines in 1 file changed: 0 ins; 30 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2277.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2277/head:pull/2277

PR: https://git.openjdk.java.net/jdk/pull/2277