Replacing deprecated <licenseUrl> with <license>

(cherry picked from commit 661e92929fa7f1d4ad8de934d4cc0e02f1c16e89)

Source commit: 4a8ee8765d1cad2b957446d7f9b5fc61f2614bd9

deployment/WinSCPnet.nuspec

@@ -6,7 +6,7 @@
     <title>WinSCP .NET assembly</title>
     <authors>Martin Prikryl</authors>
     <owners>Martin Prikryl</owners>
-    <licenseUrl>https://www.mozilla.org/MPL/2.0/</licenseUrl>
+    <license type="expression">MPL-2.0</license>
     <projectUrl>https://winscp.net/eng/docs/library</projectUrl>
     <iconUrl>https://winscp.net/pad/winscp.png</iconUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>