docs: correct plugin name in basic-auth documentation (#11481) #2

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	39m 41s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	35m 8s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	25m 51s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	26m 54s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	42m 6s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	36m 0s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	26m 17s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	26m 39s
	4h 18m 36s

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