RFR: 8257971: (fs) Remove unused code from WindowsPath.subpath(begin, end)

[Brian Burkhalter]

Please review this trivial change to remove the useless, vestigial local variable `nelems` from `WindowsPath::subpath(int,int)`.

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Commit messages:
 - 8257971: (fs) Remove unused code from WindowsPath.subpath(begin, end)

Changes: https://git.openjdk.java.net/jdk/pull/1718/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1718&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257971
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1718.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1718/head:pull/1718

PR: https://git.openjdk.java.net/jdk/pull/1718