Loading content over SSL

Mixed Content: The page at ‘https://cdn.wpdownloadmanager.com/notice.php?wpdmvarsion=2.7.95’ was loaded over HTTPS, but requested an insecure stylesheet ‘http://fonts.googleapis.com/css?family=Source+Sans+Pro:300,900’. This request has been blocked; the content must be served over HTTPS.

I have made some changes to the links in functions.php however I cannot find this Google font link anywhere.

Where is this located ?

https://wordpress.org/plugins/download-manager/