Remove unused models file (#898)

With the move to `kagglesdk` and the generated Python bindings, a lot of
the files under
[src/kaggle/models/](https://github.com/Kaggle/kaggle-api/tree/main/src/kaggle/models)
were unused.

Also,
[ApiDatasetColumn](https://github.com/Kaggle/kagglesdk/blob/851d58d5afea0568d52338cbdb0cb6c8ce7569e2/kagglesdk/datasets/types/dataset_api_service.py#L1063)
(generated from kagglesdk) and
[DatasetColumn](https://github.com/Kaggle/kaggle-api/blob/main/src/kaggle/models/dataset_column.py)
were used interchangeably in
[kaggle_api_extended.py](https://github.com/Kaggle/kaggle-api/blob/main/src/kaggle/api/kaggle_api_extended.py).
Make sure we always use the auto-generated class and deleted the other
one.

http://b/476473628

Author: rosbo

src/kaggle/api/kaggle_api_extended.py

@@ -149,7 +149,6 @@
 from kagglesdk.models.types.model_enums import ListModelsOrderBy, ModelInstanceType, ModelFramework
 from kagglesdk.models.types.model_types import Owner
 from kagglesdk.security.types.oauth_service import IntrospectTokenRequest
-from ..models.dataset_column import DatasetColumn
 from ..models.upload_file import UploadFile
 import kagglesdk.kaggle_client
 from enum import EnumMeta
@@ -4818,11 +4817,12 @@ def process_column(self, column):
             column: A list of values in a column to be processed.
 
         Returns:
-            A DatasetColumn object.
+            An ApiDatasetColumn object.
         """
-        processed_column = DatasetColumn(
-            name=self.get_or_fail(column, "name"), description=self.get_or_default(column, "description", "")
-        )
+        processed_column = ApiDatasetColumn()
+        processed_column.name = self.get_or_fail(column, "name")
+        processed_column.description = self.get_or_default(column, "description", "")
+
         if "type" in column:
             original_type = column["type"].lower()
             processed_column.original_type = original_type