Fix benign typo

This was benign because imports are already relative to the importing
project and the misspelling of MSBuildThisFileDirectory evaluated to
empty.

Author: nguerrera

src/Tasks/Microsoft.NET.Build.Tasks/build/Microsoft.NET.Sdk.BeforeCommon.targets

@@ -15,7 +15,7 @@ Copyright (c) .NET Foundation. All rights reserved.
     <MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
   </PropertyGroup>
 
-  <Import Project="$(MSBuildThisFileDriectory)Microsoft.NET.DefaultAssemblyInfo.targets" />
+  <Import Project="$(MSBuildThisFileDirectory)Microsoft.NET.DefaultAssemblyInfo.targets" />
 
   <!-- Set default intermediate and output paths -->
   <Import Project="$(MSBuildThisFileDirectory)Microsoft.NET.DefaultOutputPaths.targets" />