Don't use the nuget packages directory as fallback.

.. because we explicitly set `NUGET_PACKAGES` envvar now.

Author: radical

src/mono/wasm/Wasm.Build.Tests/data/nuget7.config

@@ -3,7 +3,6 @@
   <!-- Don't use any higher level config files. -->
   <fallbackPackageFolders>
     <clear />
-    <add key="local" value=".nuget" />
   </fallbackPackageFolders>
   <packageSources>
     <clear />