RFR: 8306770: Remove obsolete version checks on Mac OS X

[Roger Riggs]

BsdFileStore no longer needs to check the os.version, it is true on supported versions.

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

Commit messages:
 - 8306770: Remove obsolete version checks on Mac OS X

Changes: https://git.openjdk.org/jdk/pull/13628/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13628&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306770
  Stats: 19 lines in 1 file changed: 0 ins; 17 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13628.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13628/head:pull/13628

PR: https://git.openjdk.org/jdk/pull/13628