[jdk11u-dev] RFR: 8258795: Update IANA Language Subtag Registry to Version 2021-05-11

[Goetz Lindenmaier]

I backport this for parity with 11.0.16-oracle.

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Commit messages:
 - Backport a259ab4a8d163ff924ba56c5da5395cec0d8c350

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/954/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=954&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258795
  Stats: 340 lines in 2 files changed: 327 ins; 0 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/954.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/954/head:pull/954

PR: https://git.openjdk.java.net/jdk11u-dev/pull/954