Merge pull request #3682 from oliver-sanders/fix-python-url

cfgspec: fix broken url

cylc/flow/cfgspec/suite.py

@@ -950,7 +950,7 @@
                 `String Formatting Operations in the Python
                 documentation
                 <https://docs.python.org/3/library/stdtypes.html
-                #string-formatting>`_.
+                #printf-style-string-formatting>`_.
 
                 Additional information can be passed to event handlers via the
                 ``[cylc] -> [[environment]]`` (but not via task