HPCC-9079 Enable "Close" on tabs

Fixes HPCC-9079

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #4219 from GordonSmith/HPCC-9079

HPCC-9079 Enable "Close" on tabs

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>