BUG: `isfile` is not a method on Path objects

This exists when using `os.path.isfile` but is the wrong method call
for `pathlib.Path` objects.

Remove duplicated import and trailing whitespace as well.

IPython/core/magics/packaging.py

@@ -13,7 +13,6 b' import shlex'
 import sys
 from pathlib import Path
 
-from pathlib import Path
 from IPython.core.magic import Magics, magics_class, line_magic
 
 
@@ -28,7 +27,7 b' def _get_conda_executable():'
     # Check if there is a conda executable in the same directory as the Python executable.
     # This is the case within conda's root environment.
     conda = Path(sys.executable).parent / "conda"
-    if conda.isfile():
+    if conda.is_file():
         return str(conda)
 
     # Otherwise, attempt to extract the executable from conda history.