Update versioning to 7.4 in Release configuration

The version number in the `Version` property of the
`PropertyGroup` for the Release configuration has been
changed from `6.1.$(Build).$(Revision)` to
`7.4.$(Build).$(Revision)`, reflecting a new major version
update from 6.x to 7.x.

Author: wforney

Directory.Build.props

@@ -54,7 +54,7 @@
     <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">
         <Build Condition="'$(DesignTimeBuild)' != 'true' OR '$(BuildingProject)' == 'true'">$([System.DateTime]::op_Subtraction($([System.DateTime]::get_Now().get_Date()),$([System.DateTime]::new(2000,1,1))).get_TotalDays())</Build>
         <Revision Condition="'$(DesignTimeBuild)' != 'true' OR '$(BuildingProject)' == 'true'">$([MSBuild]::Divide($([System.DateTime]::get_Now().get_TimeOfDay().get_TotalSeconds()), 2).ToString('F0'))</Revision>
-        <Version Condition="'$(DesignTimeBuild)' != 'true' OR '$(BuildingProject)' == 'true'">6.1.$(Build).$(Revision)</Version>
+        <Version Condition="'$(DesignTimeBuild)' != 'true' OR '$(BuildingProject)' == 'true'">7.4.$(Build).$(Revision)</Version>
     </PropertyGroup>
     <ItemGroup>
         <PackageReference Include="Microsoft.Bcl.HashCode" />