RFR: 8313948: Remove unnecessary static fields defaultUpper/defaultLower in sun.net.PortConfig

[Andrey Turbanov]

Fields can be converted to local variables in <clinit>

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Commit messages:
 - [PATCH] Remove unnecessary static fields defaultUpper/defaultLower in sun.net.PortConfig

Changes: https://git.openjdk.org/jdk/pull/14950/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14950&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313948
  Stats: 4 lines in 1 file changed: 2 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14950.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14950/head:pull/14950

PR: https://git.openjdk.org/jdk/pull/14950