RFR: build: update to JUnit 5.8.2 [v2]

[Christian Stein]

> This patch that updates JUnit Jupiter to 5.8.2 and JUnit Platform to 1.8.2.
> 
> PS: The text at https://github.com/openjdk/skara#testing reading "_JUnit 5.6.2 or later is required to run the unit tests._" seems to be out of date. Shouldn't it read like: "A recent version of JUnit 5 is..."?

Christian Stein has updated the pull request incrementally with one additional commit since the last revision:

  Update README.md

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Changes:
  - all: https://git.openjdk.java.net/skara/pull/1260/files
  - new: https://git.openjdk.java.net/skara/pull/1260/files/9bc6ad07..2c9aade7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=1260&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=1260&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/1260.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1260/head:pull/1260

PR: https://git.openjdk.java.net/skara/pull/1260