fix some typos

Signed-off-by: cuishuang <imcusg@gmail.com>

Author: cuishuang

src/cli/self_update.rs

@@ -311,7 +311,7 @@ tools, but otherwise, install the C++ build tools before proceeding.
 #[cfg(windows)]
 static MSVC_AUTO_INSTALL_MESSAGE: &str = r#"# Rust Visual C++ prerequisites
 
-Rust requires a linker and Windows API libraries but they don't seem to be avaliable.
+Rust requires a linker and Windows API libraries but they don't seem to be available.
 
 These components can be acquired by installing Visual Studio.
 

src/diskio/mod.rs

@@ -411,7 +411,7 @@ pub(crate) fn write_file_incremental<P: AsRef<Path>, F: Fn(usize)>(
     if let IncrementalFile::ThreadedReceiver(recv) = content_callback {
         loop {
             // We unwrap here because the documented only reason for recv to fail is a close by the sender, which is reading
-            // from the tar file: a failed read there will propogate the error in the main thread directly.
+            // from the tar file: a failed read there will propagate the error in the main thread directly.
             let contents = recv.recv().unwrap();
             let len = contents.len();
             // Length 0 vector is used for clean EOF signalling.

tests/cli-v2.rs

@@ -1427,7 +1427,7 @@ info: installing component 'rustc'
     });
 }
 
-/// Invalidates the signature on the manifest of the nigthly channel.
+/// Invalidates the signature on the manifest of the nightly channel.
 fn make_signature_invalid(config: &Config) {
     let manifest_path = config.distdir.join("dist/channel-rust-nightly.toml");