Update .NET Core SDK

[martincostello]

Update to the latest .NET Core SDK for Visual Studio 2019 16.1.

[codecov]

Codecov Report

Merging #88 into master will increase coverage by 0.18%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #88      +/-   ##
==========================================
+ Coverage    90.8%   90.98%   +0.18%     
==========================================
  Files          21       21              
  Lines        1620     1620              
  Branches      128      128              
==========================================
+ Hits         1471     1474       +3     
+ Misses        109      106       -3     
  Partials       40       40

Impacted Files	Coverage Δ
src/SqlLocalDb/TemporarySqlLocalDbInstance.cs	97.56% <0%> (+3.65%)	⬆️

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