Fix copy file operation

[mahendrapaipuri]

jupyter-fs's MetaManager is overriding the copy method of AsyncContentsManager. But the method get is asynchronous and hence the operation fails with following stack trace:

HTTPServerRequest(protocol='https', host='redacted', method='POST', uri='/user/redacted/jupyter_0/api/contents/tests?1715595030371', version='HTTP/1.1', remote_ip='redacted')
Traceback (most recent call last):
  File "/redacted/lib/python3.11/site-packages/tornado/web.py", line 1790, in _execute
    result = await result
             ^^^^^^^^^^^^
  File "/redacted/lib/python3.11/site-packages/jupyter_server/auth/decorator.py", line 73, in inner
    return await out
           ^^^^^^^^^
  File "/redacted/lib/python3.11/site-packages/jupyter_server/services/contents/handlers.py", line 278, in post
    await self._copy(copy_from, path)
  File "/redactedlib/python3.11/site-packages/jupyter_server/services/contents/handlers.py", line 216, in _copy
    model = await ensure_async(self.contents_manager.copy(copy_from, copy_to))
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/redacted/lib/python3.11/site-packages/jupyter_core/utils/__init__.py", line 198, in ensure_async
    result = await obj
             ^^^^^^^^^
  File "/redacted/lib/python3.11/site-packages/jupyterfs/metamanager.py", line 177, in copy
    model.pop("path", None)
    ^^^^^^^^^
AttributeError: 'coroutine' object has no attribute 'pop'
[W 2024-05-13 12:10:30.398 ServerApp] wrote error: 'Unhandled error'
    Traceback (most recent call last):
      File "/redacted/lib/python3.11/site-packages/tornado/web.py", line 1790, in _execute
        result = await result
                 ^^^^^^^^^^^^
      File "/redacted/lib/python3.11/site-packages/jupyter_server/auth/decorator.py", line 73, in inner
        return await out
               ^^^^^^^^^
      File "/redacted/lib/python3.11/site-packages/jupyter_server/services/contents/handlers.py", line 278, in post
        await self._copy(copy_from, path)
      File "/redacted/lib/python3.11/site-packages/jupyter_server/services/contents/handlers.py", line 216, in _copy
        model = await ensure_async(self.contents_manager.copy(copy_from, copy_to))
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/redacted/lib/python3.11/site-packages/jupyter_core/utils/__init__.py", line 198, in ensure_async
        result = await obj
                 ^^^^^^^^^
      File "/redacted/lib/python3.11/site-packages/jupyterfs/metamanager.py", line 177, in copy
        model.pop("path", None)
        ^^^^^^^^^
    AttributeError: 'coroutine' object has no attribute 'pop'
/redacted/lib/python3.11/site-packages/tornado/web.py:1801: RuntimeWarning: coroutine 'path_first_arg.<locals>._wrapper' was never awaited
  if self._prepared_future is not None and not self._prepared_future.done():
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

Seems like the overloaded method is vestigial and this PR removes that part of the code.

[github-actions]

Launch a binder notebook on branch mahendrapaipuri/jupyter-fs/fix_copy