Fix license

Author: Alex Khil

src/IpData/IpData.nuspec

@@ -6,7 +6,7 @@
     <authors>IpData Contributors</authors>
     <owners>IpData Contributors</owners>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
-    <license type="expression">MIT</license>
+    <licenseUrl>https://licenses.nuget.org/MIT</licenseUrl>
     <projectUrl>https://github.com/alexkhil/IpData</projectUrl>
     <iconUrl>https://image.ibb.co/iDQdUS/ipdatalogo.png</iconUrl>
     <description>C# library to gather information for an IP using ipdata.co</description>