fix: don't wrap SpannerDate so timezone does not affect results

[prunge-helix]

This change allows the should use an ARRAY query parameter to query record from the Venues example table test to pass when run on machines with time zones with positive offsets.

Fixes #710

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[codecov]

Codecov Report

Merging #711 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #711   +/-   ##
=======================================
  Coverage   97.81%   97.81%           
=======================================
  Files          15       15           
  Lines        1648     1648           
  Branches      278      278           
=======================================
  Hits         1612     1612           
  Misses         19       19           
  Partials       17       17

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[prunge-helix]

@googlebot I signed it!

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[bcoe]

@prunge-helix thanks for the patch 😄

I think this would be a breaking change, so we need to be a bit careful pulling it in. I've looped in @stephenplusplus and @callmehiphop who know more about @google-cloud/spanner than myself.

[callmehiphop]

@bcoe why would this be a breaking change? It looks like it is just a fix for a sample

[bcoe]

@callmehiphop @prunge-helix my bad, I didn't notice it was a sample file changing 😄

please go ahead and land.