RFR: 7903958: JTHarness 6.0 does not show "Test Run Messages" tab correctly

[Dmitry Bessonov]

- src/com/sun/javatest/exec/i18n.properties is missing `html.lang=en`
 - HTMLWriterEx.META_CONTENT template string contains a typo which leads to generation of an incorrect HTML tag

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Commit messages:
 - 7903958: JTHarness 6.0 does not show "Test Run Messages" tab correctly

Changes: https://git.openjdk.org/jtharness/pull/92/files
  Webrev: https://webrevs.openjdk.org/?repo=jtharness&pr=92&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903958
  Stats: 3 lines in 2 files changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jtharness/pull/92.diff
  Fetch: git fetch https://git.openjdk.org/jtharness.git pull/92/head:pull/92

PR: https://git.openjdk.org/jtharness/pull/92