docs(import_datasources): Remove legacy documentation and update current use

docs/docs/miscellaneous/importing-exporting-datasources.mdx

@@ -61,15 +61,29 @@ superset export_datasource_schema
 
 As a reminder, you can use the `-b` flag to include back references.
 
-### Importing Datasources from YAML
+### Importing Datasources
 
-In order to import datasources from a YAML file(s), run:
+In order to import datasources from a ZIP file, run:
+
+```
+superset import_datasources -p <path / filename>
+```
+
+The optional username flag **-u** sets the user used for the datasource import. The default is 'admin'. Example:
+
+```
+superset import_datasources -p <path / filename> -u 'admin'
+```
+
+### Legacy Importing Datasources from YAML
+
+In Superset 4 the older way of datasource importing is supported as `legacy_import_datasources`. In older versions (2 & 3) of Superset, to switch between ZIP and YAML files, the feature flag `VERSIONED_EXPORT` is used. When `VERSIONED_EXPORT` is `True`, `import_datasources` expects a ZIP file, otherwise YAML. Example:
 
 ```
 superset import_datasources -p <path or filename>
 ```
 
-If you supply a path all files ending with **yaml** or **yml** will be parsed. You can apply
+When `VERSIONED_EXPORT` is `False`, if you supply a path all files ending with **yaml** or **yml** will be parsed. You can apply
 additional flags (e.g. to search the supplied path recursively):
 
 ```