chore(csharp): Bump System.Net.Http.WinHttpHandler to 8.0.3 (#3013)

Performed the following updates:
- Updated System.Net.Http.WinHttpHandler from 8.0.2 to 8.0.3 in
/csharp/Directory.Build.props, /csharp/Directory.Build.targets,
/csharp/src/Drivers/BigQuery/Apache.Arrow.Adbc.Drivers.BigQuery.csproj
- Updated System.Net.Http.WinHttpHandler from 8.0.2 to 8.0.3 in
/csharp/Directory.Build.props, /csharp/Directory.Build.targets,
/csharp/src/Drivers/FlightSql/Apache.Arrow.Adbc.Drivers.FlightSql.csproj

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csharp/src/Drivers/BigQuery/Apache.Arrow.Adbc.Drivers.BigQuery.csproj

@@ -4,7 +4,7 @@
     <PackageReadmeFile>readme.md</PackageReadmeFile>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="System.Net.Http.WinHttpHandler" Version="8.0.2" Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'" />
+    <PackageReference Include="System.Net.Http.WinHttpHandler" Version="8.0.3" Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'" />
     <PackageReference Include="Google.Cloud.BigQuery.Storage.V1" Version="3.17.0" />
     <PackageReference Include="Google.Cloud.BigQuery.V2" Version="3.11.0" />
   </ItemGroup>

csharp/src/Drivers/FlightSql/Apache.Arrow.Adbc.Drivers.FlightSql.csproj

@@ -3,7 +3,7 @@
     <TargetFrameworks>netstandard2.0;net6.0</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="System.Net.Http.WinHttpHandler" Version="8.0.2" Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'" />
+    <PackageReference Include="System.Net.Http.WinHttpHandler" Version="8.0.3" Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'" />
     <PackageReference Include="Apache.Arrow.Flight" Version="20.0.0" />
   </ItemGroup>
   <ItemGroup>