Update Package.nuspec

We bumped the package dependency to NewtonSoft 13.0.1 but forgot to update the nuspec file.

Package.nuspec

@@ -13,7 +13,7 @@
     <tags>sourcemap callstack stackframe deminify</tags>
     <dependencies>
       <dependency id="AjaxMin" version="5.14.5506.26202" />
-      <dependency id="Newtonsoft.Json" version="9.0.1" />
+      <dependency id="Newtonsoft.Json" version="13.0.1" />
     </dependencies>
   </metadata>
   <files>
@@ -22,4 +22,4 @@
     <file src="src\SourcemapToolkit.SourcemapParser\bin\Release\SourcemapToolkit.SourcemapParser.dll" target="lib\net40" />
     <file src="src\SourcemapToolkit.SourcemapParser\bin\Release\SourcemapToolkit.SourcemapParser.pdb" target="lib\net40" />
   </files>
-</package>
+</package>