DOC: Fix apply_function shape description for Epochs

The fun parameter docstring for mne.Epochs.apply_function incorrectly stated
that the array passed to the user's function when channel_wise=False has
shape (len(picks), n_times). The actual shape is (n_epochs, n_channels, n_times).

Adds a new fun_applyfun_epochs docdict entry alongside fun_applyfun_evoked
and fun_applyfun_stc, leaving the Raw docstring (where (len(picks), n_times)
is correct) untouched. Per scott-huberty's review suggestion on #13136.

Fixes #13118

Author: bkowshik

mne/epochs.py

@@ -1974,7 +1974,7 @@ def apply_function(
 
         Parameters
         ----------
-        %(fun_applyfun)s
+        %(fun_applyfun_epochs)s
         %(picks_all_data_noref)s
         %(dtype_applyfun)s
         %(n_jobs)s Ignored if ``channel_wise=False`` as the workload

mne/utils/docs.py

@@ -1919,6 +1919,9 @@ def _reflow_param_docstring(docstring, has_first_line=True, width=75):
 docdict["fun_applyfun"] = applyfun_fun_base.format(
     " if ``channel_wise=True`` and ``(len(picks), n_times)`` otherwise"
 )
+docdict["fun_applyfun_epochs"] = applyfun_fun_base.format(
+    " if ``channel_wise=True`` and ``(n_epochs, n_channels, n_times)`` otherwise"
+)
 docdict["fun_applyfun_evoked"] = applyfun_fun_base.format(
     " because it will apply channel-wise"
 )