DOC: fix depwarn message to tell user to use Query |> sink not query …

[sglyon]

…|> sink

[codecov-io]

Codecov Report

Merging #120 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #120   +/-   ##
=======================================
  Coverage   87.07%   87.07%           
=======================================
  Files           5        5           
  Lines         147      147           
=======================================
  Hits          128      128           
  Misses         19       19

Impacted Files	Coverage Δ
src/MySQL.jl	82.14% <100%> (ø)	⬆️

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[quinnj]

Thanks!