Exclude Data namespace from dotnet code coverage

DbContext/EF configuration classes are infra plumbing with no
business logic to unit test; counting them against the coverage
target only dilutes the signal, same rationale as Migrations.

tests/api/MicCheck.Api.Tests.Unit/coverlet.runsettings

@@ -4,7 +4,7 @@
     <DataCollectors>
       <DataCollector friendlyName="XPlat code coverage">
         <Configuration>
-          <Exclude>[MicCheck.Api]MicCheck.Api.Migrations.*</Exclude>
+          <Exclude>[MicCheck.Api]MicCheck.Api.Migrations.*,[MicCheck.Api]MicCheck.Api.Data.*</Exclude>
         </Configuration>
       </DataCollector>
     </DataCollectors>