Bump redis example app Ruby 2.6.0
Bump redis example app Ruby 2.6.0

[#168034620]

Signed-off-by: James Norman <ee17c86653c1b33db95db3d5b42fdcc2c8764b22@pivotal.io>

pivotal-cf/cf-redis-smoke-tests,pivotal-cf/cf-redis-smoke-tests