test-path-utils.c: remove incorrect assumption

test-path-utils.c: remove incorrect assumption

In normalize_ceiling_entry(), we test that normalized paths end with
slash, *unless* the path to be normalized was already the root
directory.

However, normalize_path_copy() does not even enforce this condition.

Even worse: on Windows, the root directory gets translated into a
Windows directory by the Bash before being passed to `git.exe` (or
`test-path-utils.exe`), which means that we cannot even know whether
the path that was passed to us was the root directory to begin with.

This issue has already caused endless hours of trying to "fix" the
MSYS2 runtime, only to break other things due to MSYS2 ensuring that
the converted path maintains the same state as the input path with
respect to any final '/'.

So let's just forget about this test. It is non-essential to Git's
operation, anyway.

Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Ray Donnelly <mingw.android@gmail.com>