Clarify to_unix_separators{,_on_windows} relationship

`to_native_path_on_windows` already called `to_windows_separators`
to do what would otherwise repeat logic of `to_windows_separators`,
but `to_unix_separators_on_windows` repeated the code of
`to_unix_separators`. Having `to_unix_separators_on_windows` call
`to_unix_separators` instead of repeating its logic seems slightly
easier to read, elucidates the relationship between the several
functions, and might be slightly more maintainable.

This is purely a refactoring, which should not change the effect.
It should also not change performance, since the compiler should be
able to inline the call in circumstnaces where that would help.

Author: EliahKagan

gix-path/src/convert.rs

@@ -222,7 +222,7 @@ pub fn to_native_path_on_windows<'a>(path: impl Into<Cow<'a, BStr>>) -> Cow<'a,
 pub fn to_unix_separators_on_windows<'a>(path: impl Into<Cow<'a, BStr>>) -> Cow<'a, BStr> {
     #[cfg(windows)]
     {
-        replace(path, b'\\', b'/')
+        to_unix_separators(path)
     }
     #[cfg(not(windows))]
     {