RFR: 8293009: Remove unused field 'millisPerHour' in DateFormatSymbols

[Andrey Turbanov]

Field `java.text.DateFormatSymbols#millisPerHour` is unused. It was unused in initial OpenJDK sources.

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Commit messages:
 - [PATCH] Unused field DateFormatSymbols.millisPerHour

Changes: https://git.openjdk.org/jdk/pull/10005/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10005&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293009
  Stats: 6 lines in 1 file changed: 0 ins; 5 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10005.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10005/head:pull/10005

PR: https://git.openjdk.org/jdk/pull/10005