CSHARP-4667: Updated the nuspec reference to LICENSE.md. (#1106)

Author: JamesKovacs

src/Directory.Build.props

@@ -19,7 +19,7 @@
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
     <PackageProjectUrl>https://www.mongodb.com/docs/drivers/csharp/</PackageProjectUrl>
     <PackageTags>mongodb;mongo;nosql</PackageTags>
-    <PackageLicenseFile>License.txt</PackageLicenseFile>
+    <PackageLicenseFile>LICENSE.md</PackageLicenseFile>
     <PackageLanguage>en-US</PackageLanguage>
     <IncludeSymbols>true</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
@@ -48,7 +48,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <None Include="..\..\License.txt" Pack="true" PackagePath="$(PackageLicenseFile)" />
+    <None Include="..\..\LICENSE.md" Pack="true" PackagePath="$(PackageLicenseFile)" />
     <None Include="..\..\packageIcon.png" Pack="true" PackagePath="" />
   </ItemGroup>
 </Project>