RFR: 7093322: (fs spec) Files.newBufferedWriter should be clear when coding errors are detected

[Brian Burkhalter]

Add a sentence to clarify that coding exceptions are not thrown until the characters are actually written to the underlying stream.

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Commit messages:
 - 7093322: (fs spec) Files.newBufferedWriter should be clear when coding errors are detected

Changes: https://git.openjdk.org/jdk/pull/11616/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11616&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-7093322
  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11616.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11616/head:pull/11616

PR: https://git.openjdk.org/jdk/pull/11616