Bump log4net in /csharp/Adapter/Microsoft.Spark.CSharp

Bumps [log4net](https://github.com/apache/logging-log4net) from 2.0.5 to 2.0.10.
- [Release notes](https://github.com/apache/logging-log4net/releases)
- [Commits](https://github.com/apache/logging-log4net/commits/rel/2.0.10)

---
updated-dependencies:
- dependency-name: log4net
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

csharp/Adapter/Microsoft.Spark.CSharp/Adapter.csproj

@@ -40,8 +40,9 @@
     <StartupObject />
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="log4net">
-      <HintPath>..\..\packages\log4net.2.0.5\lib\net45-full\log4net.dll</HintPath>
+    <Reference Include="log4net, Version=2.0.9.0, Culture=neutral, PublicKeyToken=669e0ddf0bb1aa2a">
+      <HintPath>..\..\packages\log4net.2.0.10\lib\net45\log4net.dll</HintPath>
+      <Private>True</Private>
     </Reference>
     <Reference Include="Newtonsoft.Json">
       <HintPath>..\..\packages\Newtonsoft.Json.7.0.1\lib\net45\Newtonsoft.Json.dll</HintPath>

csharp/Adapter/Microsoft.Spark.CSharp/packages.config

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="log4net" version="2.0.5" targetFramework="net45" />
+  <package id="log4net" version="2.0.10" targetFramework="net45" />
   <package id="Newtonsoft.Json" version="7.0.1" targetFramework="net45" />
   <package id="Razorvine.Pyrolite" version="4.10.0" targetFramework="net45" />
   <package id="Razorvine.Serpent" version="1.12.0" targetFramework="net45" />
-</packages>
+</packages>