RFR: 7509: Add 2021-09 target platform [v2]

[Marcus Hirt]

> ...also updating babel.

Marcus Hirt has updated the pull request incrementally with one additional commit since the last revision:

  Fixed version

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Changes:
  - all: https://git.openjdk.java.net/jmc/pull/357/files
  - new: https://git.openjdk.java.net/jmc/pull/357/files/5189ace9..9102dd49

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=357&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=357&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jmc/pull/357.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/357/head:pull/357

PR: https://git.openjdk.java.net/jmc/pull/357