Fix interval keyword argument in oedi_9068 gallery example

Fixes #2791.

The oedi_9068 gallery example calls get_nsrdb_psm4_conus() with
interval=5, but the function's parameter is named time_step (the
interval name comes from the NSRDB API query string, not the Python
signature). This was missed when PR #2582 migrated the example from
get_psm3 (which used interval) to get_nsrdb_psm4_conus (which uses
time_step).

Changes interval=5 to time_step=5 in the example call.

No test changes needed — test_get_nsrdb_psm4_conus_5min already
exercises time_step=5 against the function directly.

Author: karlhillx

docs/examples/system-models/oedi_9068.py

@@ -145,7 +145,8 @@
         'albedo', 'precipitable_water']
 psm3, psm3_metadata = pvlib.iotools.get_nsrdb_psm4_conus(latitude, longitude,
                                                          api_key, email,
-                                                         year=2019, interval=5,
+                                                         year=2019,
+                                                         time_step=5,
                                                          parameters=keys,
                                                          map_variables=True,
                                                          leap_day=True)

docs/sphinx/source/whatsnew/v0.15.3.rst

@@ -23,6 +23,9 @@ Enhancements
 Documentation
 ~~~~~~~~~~~~~
 
+* Fixed broken ``interval`` keyword argument in the ``oedi_9068`` gallery
+  example; the correct parameter name is ``time_step``. (:issue:`2791`)
+
 
 Testing
 ~~~~~~~