Bump RestSharp to 106.15.0

Fixes #1400

src/Directory.Packages.props

@@ -32,8 +32,8 @@
     <PackageVersion Include="NUnit" Version="3.13.2" />
     <PackageVersion Include="NunitXml.TestLogger" Version="3.0.117" />
     <PackageVersion Include="PdfSharpCore" Version="1.3.9" />
-    <PackageVersion Include="RestSharp.Serializers.SystemTextJson" Version="106.13.0" />
-    <PackageVersion Include="RestSharp" Version="106.13.0" />
+    <PackageVersion Include="RestSharp.Serializers.SystemTextJson" Version="106.15.0" />
+    <PackageVersion Include="RestSharp" Version="106.15.0" />
     <PackageVersion Include="Selenium.Support" Version="3.141.0" />
     <PackageVersion Include="Selenium.WebDriver.ChromeDriver" Version="91.0.4472.10100" />
     <PackageVersion Include="Sentry" Version="3.11.1" />