Fixed typo in ImapClientDemo.Android sample

samples/ImapClientDemo.Android/ImapClientDemo.Android/LoginActivity.cs

@@ -80,7 +80,7 @@ async void buttonLogin_Click (object sender, EventArgs e)
 						"need to go into your GMail settings to enable \"less secure apps\" in order " + 
 						"to get this demo to work.\n\n" +
 						"For a real Mail application, you'll want to add support for obtaining the " +
-						"user's OAuth2 credentials to prevent the need for user's to enable this, but " +
+						"user's OAuth2 credentials to prevent the need for users to enable this, but " +
 						"that is beyond the scope of this demo.",
 						ToastLength.Long).Show ();
 				}