RFR: 8278137: JFR: PrettyWriter uses incorrect year specifier

[Aleksey Shipilev]

Found by SonarCloud, actually. For this commit: https://github.com/openjdk/jdk/commit/ee3576a48b700df3d8ad4bd447346d4102b20818 -- it says:

> Week Year ("YYYY") should not be used for date formatting
> 
> Few developers are aware of the difference between Y for "Week year" and y for Year when formatting and parsing a date with SimpleDateFormat or DateTimeFormatter. That's likely because for most dates, Week year and Year are the same, so testing at any time other than the first or last week of the year will yield the same value for both y and Y. But in the last week of December and the first week of January, you may get unexpected results.

See also ErrorProne rule: https://errorprone.info/bugpattern/MisusedWeekYear

A nice end-of-the-year time-bomb, that :)

Additional testing:
 - [x] Linux x86_64 fastdebug `jdk_jfr`

-------------

Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/6665/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6665&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278137
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6665.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6665/head:pull/6665

PR: https://git.openjdk.java.net/jdk/pull/6665