RFR: Fix jcheck whitespace checks so they make sense for the Guide

[Magnus Ihse Bursie]

The whitespace file filter in .jcheck/conf had just been copied from a java-based project...

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Commit messages:
 - Fix jcheck whitespace checks so they make sense for the Guide

Changes: https://git.openjdk.java.net/guide/pull/48/files
 Webrev: https://webrevs.openjdk.java.net/?repo=guide&pr=48&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/guide/pull/48.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/48/head:pull/48

PR: https://git.openjdk.java.net/guide/pull/48