fix(ai-proxy): remove `passthrough` #1219

Job	Run time
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/http3/admin)	14m 48s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	34m 40s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	33m 0s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yam...	23m 57s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script...	24m 15s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/http3/admin)	13m 26s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	33m 26s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	34m 4s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/con...	24m 18s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secr...	25m 34s
	4h 21m 28s

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