fix(grpc-web): response contains two trailer chunks #1154

Job	Run time
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/http3/admin)	13m 39s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	17m 27s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	37m 13s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yam...	24m 40s
build (ubuntu-latest, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script...	26m 45s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/http3/admin)	14m 3s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	18m 19s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	33m 56s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/con...	26m 3s
build (ubuntu-latest, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secr...	25m 2s
	3h 57m 7s

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