fix(ci): pip installation failures #17060

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	16m 55s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	18m 41s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	20m 35s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	16m 53s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	18m 1s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	17m 13s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	16m 53s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	15m 25s
	2h 20m 36s

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