docs: Update docs on TEST single test run.
docs: Update docs on TEST single test run.

The Contributing docs now clarify how to run a single test.

Signed-off-by: Fedor Indutny <e39d94bae70283f13d24c278e04952d6dad9384b@indutny.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node