update readme with 7.16.0 #81

Job	Run time
Build stack projects (samples/server/petstore/haskell-yesod/)	12m 38s
Build stack projects (samples/client/petstore/haskell-http-client/)	9m 50s
Build stack projects (samples/server/others/haskell-servant-ping/)	12m 7s
Build stack projects (samples/server/petstore/haskell-servant/)	12m 41s
	47m 16s

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