Port open_parent_dir to fs_utf8 and cap-async-std.

Author: sunfishcode

cap-async-std/src/fs_utf8/dir.rs

@@ -619,10 +619,7 @@ impl Dir {
     ///
     /// This function accesses a directory outside of the `self` subtree.
     #[inline]
-    pub async fn open_parent_dir<P: AsRef<Utf8Path>>(
-        &self,
-        ambient_authority: AmbientAuthority,
-    ) -> io::Result<Self> {
+    pub async fn open_parent_dir(&self, ambient_authority: AmbientAuthority) -> io::Result<Self> {
         self.cap_std
             .open_parent_dir(ambient_authority)
             .await

cap-std/src/fs_utf8/dir.rs

@@ -604,10 +604,7 @@ impl Dir {
     ///
     /// This function accesses a directory outside of the `self` subtree.
     #[inline]
-    pub fn open_parent_dir<P: AsRef<Utf8Path>>(
-        &self,
-        ambient_authority: AmbientAuthority,
-    ) -> io::Result<Self> {
+    pub fn open_parent_dir(&self, ambient_authority: AmbientAuthority) -> io::Result<Self> {
         self.cap_std
             .open_parent_dir(ambient_authority)
             .map(Self::from_cap_std)