RFR: 8276947: Clarify how DateTimeFormatterBuilder.appendFraction handles value ranges

[Claes Redestad]

This changes the specification of `DateTimeFormatterBuilder.appendFraction` to more clearly specify that the formatter will throw an exception if you attempt to print a value outside of the value range of the given field. Changes suggested by @jodastephen in #6188.

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Commit messages:
 - Clarify how DateTimeFormatterBuilder.appendFraction handles value ranges

Changes: https://git.openjdk.java.net/jdk/pull/6335/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6335&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276947
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6335.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6335/head:pull/6335

PR: https://git.openjdk.java.net/jdk/pull/6335