fix(ci): pip installation failures #830

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/http3/admin)	20m 8s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	17m 35s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	18m 53s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	16m 58s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	15m 23s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/http3/admin)	15m 38s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	17m 0s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	18m 51s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	15m 8s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	15m 5s
	2h 50m 39s

Provide feedback