Fixing unit test configurations in order to fix Windows official builds (#1580)

global.json

@@ -4,7 +4,7 @@
     "runtimes": {
       "dotnet/x64": [
         "2.1.25",
-        "5.0.3"
+        "5.0.7"
       ]
     }
   },

src/devices/Amg88xx/tests/Amg88xx.Tests.csproj

 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net5.0;netcoreapp2.1</TargetFrameworks>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
     <IsPackable>false</IsPackable>
     <GenerateDocumentationFile>false</GenerateDocumentationFile>
   </PropertyGroup>

src/devices/Arduino/tests/Arduino.Tests.csproj

 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net5.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp2.1</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <LangVersion>latest</LangVersion>
     <GenerateDocumentationFile>false</GenerateDocumentationFile> 

src/devices/SensorHub/tests/SensorHub.Tests.csproj

 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
     <LangVersion>9</LangVersion>
     <IsPackable>false</IsPackable>
     <GenerateDocumentationFile>false</GenerateDocumentationFile>