Remove TODOs about using path-slash to handle escapes

The `to_unix_separators` and `to_windows_separators` functions in
`gix_path::convert` had TODO comments saying they should use the
`path-slash` crate "to handle escapes". These comments were added
as part of e4f4c4b (#397) but the context there and in the broader
related issue #301 does not seem to clarify the basis for this.

It is not really clear what handling escapes would entail here, and
it seems like there is not a way to do it without substantially
changing the interface of these conversion functions in `gix-path`,
which currently take a single argument representing a path and
return a single string-like value also representing a path. If
escape sequences appaer in the input to such a path conversion
function, it would not have a way to know if they are meant
literally or as escape sequences. (An analogous concern applies if
a function is to add escape sequences in its return value; it would
have no way to know if the caller expects them.)

Furthermore, while `path-slash` can convert some `\` paths to use
`/` instead, it does not appear to do anything related to handling
escape sequencs or distinguishing which occurrences of `\` or any
other character may be intended as part of an escape sequence.
Its documentation does prominently mention that `\` in escape
sequnces should not be converted to `/`:

> On Unix-like OS, the path separator is `/`. So any conversion is
> not necessary. But on Windows, the file path separator is `\`,
> and needs to be replaced with `/` for converting the paths to
> "slash paths". Of course, `\`s used for escaping characters
> should not be replaced.

But it looks like the part about `\` characters used for escaping
is meant as advice on how and when to use `path-slash`, rather than
meaning that `path-slash` would itself be able to distinguish
between `\` characters meant as directory separators and `\`
characters that perform quoting/escaping.

gix-path/src/convert.rs

@@ -232,15 +232,13 @@ pub fn to_unix_separators_on_windows<'a>(path: impl Into<Cow<'a, BStr>>) -> Cow<
 /// Replaces windows path separators with slashes, unconditionally.
 ///
 /// **Note** Do not use these and prefer the conditional versions of this method.
-// TODO: use https://lib.rs/crates/path-slash to handle escapes
 pub fn to_unix_separators<'a>(path: impl Into<Cow<'a, BStr>>) -> Cow<'a, BStr> {
     replace(path, b'\\', b'/')
 }
 
 /// Find backslashes and replace them with slashes, which typically resembles a unix path, unconditionally.
 ///
 /// **Note** Do not use these and prefer the conditional versions of this method.
-// TODO: use https://lib.rs/crates/path-slash to handle escapes
 pub fn to_windows_separators<'a>(path: impl Into<Cow<'a, BStr>>) -> Cow<'a, BStr> {
     replace(path, b'/', b'\\')
 }