RFR: CODETOOLS-7903244: Add FAQ entry about accessing JUnit and TestNG libraries

[Jonathan Gibbons]

Please review an update to the jtreg FAQ, on how to determine the location of the TestNG and JUnit jar files.

(The underlying need is because we have  changed the names of these jar files in jtreg 7, to be the base name of the jar file provided when building jjtreg, which may contain the version number. Thus, tests should no longer assume a simple name like unit.jar and testng.jar.)

In addition, while editing the file, the IDE removed some redundant end-of-line spaces.

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Commit messages:
 - CODETOOLS-7903244: Add FAQ entry about accessing JUnit and TestNG libraries

Changes: https://git.openjdk.org/jtreg/pull/99/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=99&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903244
  Stats: 41 lines in 1 file changed: 31 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jtreg/pull/99.diff
  Fetch: git fetch https://git.openjdk.org/jtreg pull/99/head:pull/99

PR: https://git.openjdk.org/jtreg/pull/99