RFR: 6940: build.sh test arguments wrong

[Patrick Reinhart]

Align the help with the actual accepted arguments

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Commit messages:
 - 6940: Updated help to align with the actual accepted test arguments

Changes: https://git.openjdk.java.net/jmc/pull/129/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=129&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6940
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jmc/pull/129.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/129/head:pull/129

PR: https://git.openjdk.java.net/jmc/pull/129