HPCC-11574 Replace Playground tab with ECL tab

Fixes HPCC-11574

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #6402 from GordonSmith/HPCC-11574

HPCC-11574 Replace Playground tab with ECL tab

Reviewed-By: Miguel Vazquez <miguel.vazquez@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>