Fix outdatede references in the documentation
Correct the docs reference to the old name of the extract_number and remove the nonexisting convert_number reference.
@@ -17,9 +17,9 @@ extract_datetime
----------------
.. autofunction:: mycroft.util.extract_datetime
-extractnumber
+extract_number
-------------
-.. autofunction:: mycroft.util.extractnumber
+.. autofunction:: mycroft.util.extract_number
normalize
---------
@@ -29,10 +29,6 @@ nice_number
-----------
.. autofunction:: mycroft.util.nice_number
-convert_number
---------------
-.. autofunction:: mycroft.util.convert_number
-
resolve_resource_file
---------------------
.. autofunction:: mycroft.util.resolve_resource_file
