fix: grpc-web trailers #12549

Job	Run time
run ci on centos7 (lua-resty-worker-events, t/plugin/[a-k]*)	30m 17s
run ci on centos7 (lua-resty-worker-events, t/plugin/[l-z]*)	30m 13s
run ci on centos7 (lua-resty-worker-events, t/admin t/cli t/config-center-yaml t/control t/core t...	23m 29s
run ci on centos7 (lua-resty-worker-events, t/node t/pubsub t/router t/script t/secret t/stream-n...	21m 21s
run ci on centos7 (lua-resty-events, t/plugin/[a-k]*)	31m 2s
run ci on centos7 (lua-resty-events, t/plugin/[l-z]*)	30m 10s
run ci on centos7 (lua-resty-events, t/admin t/cli t/config-center-yaml t/control t/core t/debug ...	23m 26s
run ci on centos7 (lua-resty-events, t/node t/pubsub t/router t/script t/secret t/stream-node t/u...	21m 25s
	3h 31m 23s

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