Update to cap-std 0.24.1, fixing compilation on Right nightly. (#3786)

Other than doc updates, this just contains bytecodealliance/cap-std#235,
a fix for compilation errors on Rust nightly that look like this:

```
error[E0308]: mismatched types
  --> cap-primitives/src/fs/via_parent/rename.rs:22:58
   |
22 |     let (old_dir, old_basename) = open_parent(old_start, &old_path)?;
   |                                                          ^^^^^^^^^ expected struct `Path`, found opaque type
   |
  ::: cap-primitives/src/rustix/fs/dir_utils.rs:67:48
   |
67 | pub(crate) fn strip_dir_suffix(path: &Path) -> impl Deref<Target = Path> + '_ {
   |                                                ------------------------------ the found opaque type
   |
   = note:   expected struct `Path`
           found opaque type `impl Deref<Target = Path>`
```

crates/test-programs/Cargo.toml

@@ -21,7 +21,7 @@ tempfile = "3.1.0"
 os_pipe = "0.9"
 anyhow = "1.0.19"
 wat = "1.0.37"
-cap-std = "0.24.0"
+cap-std = "0.24.1"
 tokio = { version = "1.8.0", features = ["rt-multi-thread"] }
 
 [features]