Move dateset to dictionary_code.txt

Although it's hardly a word, it appears to have been added
to the aspell dictionary:
#2897

Not sure what the rationale for adding `dateset` to the aspell
dictionary is, but search engines show the context is usually
programming and source code, so `dictionary_code.txt` is probably
the best choice.

codespell_lib/data/dictionary.txt

@@ -11504,8 +11504,6 @@ datecreatedd->datecreated
 datection->detection
 datections->detections
 datee->date
-dateset->dataset
-datesets->datasets
 datset->dataset
 datsets->datasets
 daty->data, date,

codespell_lib/data/dictionary_code.txt

@@ -12,6 +12,8 @@ cloneable->clonable
 cmo->com
 copyable->copiable
 creat->create, crate,
+dateset->dataset
+datesets->datasets
 define'd->defined
 deque->dequeue
 doas->does, do as,