config: Fix broken link to date formatting documentation

Close #590

exampleSite/config.toml

@@ -105,7 +105,7 @@ enableGitInfo = false
   longitude = "-122.1697"
   zoom = 15
 
-  # Date and time format (refer to Go's date format: http://fuckinggodateformat.com )
+  # Date and time format (refer to https://sourcethemes.com/academic/docs/customization/#date-format )
   #   Examples: "Mon, Jan 2, 2006" or "2006-01-02"
   date_format = "Jan 2, 2006"
   #   Examples: "3:04 pm" or "15:04"
@@ -192,7 +192,7 @@ enableGitInfo = false
 
   # Configuration of publication pages.
   [params.publications]
-    # Date format (refer to Go's date format: http://fuckinggodateformat.com )
+    # Date format (refer to https://sourcethemes.com/academic/docs/customization/#date-format )
     #   Examples: "Mon, Jan 2, 2006" or "2006-01-02"
     date_format = "January, 2006"