hg: code-tools/jtreg: update copyright; tweak -retain help

[jonathan.gibbons at oracle.com]

Changeset: 60bbf225892b
Author:    jjg
Date:      2020-06-16 08:15 -0700
URL:       https://hg.openjdk.java.net/code-tools/jtreg/rev/60bbf225892b

update copyright; tweak -retain help

! src/share/classes/com/sun/javatest/regtest/tool/i18n.properties