As we now support OpenResty 1.21.4 and make it as default, time to consider dropping the support of OpenResty 1.17.8.
OpenResty 1.17.8 is released more than 2 years ago. And we have a tradition to support only the latest three versions of OpenResty, which are 1.19.3 / 1.19.9 / 1.21.4 now. By dropping the support of OpenResty 1.17.8, we can remove extra CI job and version check, making the code simpler. What about your opinion?
