Auto merge of #38648 - utkarshkukreti:question-mark-in-libstd-documentation-examples, r=pnkfelix,steveklabnik,frewsxcvx

libstd: replace all `try!` with `?` in documentation examples

See #38644.

For the record, I used the following Perl one-liner and then manually fixed a couple of things it got wrong:

    $ perl -p -i -e 's#(///.*)try!\((.*)\)#$1$2?#' src/libstd/**/*.rs

1 files changed, 2 insertions, 2 deletions

diff --git a/src/libstd/sys/windows/ext/fs.rs b/src/libstd/sys/windows/ext/fs.rs
index 7fc04ad69d6..c63dd8a47ca 100644
--- a/src/libstd/sys/windows/ext/fs.rs
+++ b/src/libstd/sys/windows/ext/fs.rs
@@ -257,7 +257,7 @@ impl MetadataExt for Metadata {
 /// use std::os::windows::fs;
 ///
 /// # fn foo() -> std::io::Result<()> {
-/// try!(fs::symlink_file("a.txt", "b.txt"));
+/// fs::symlink_file("a.txt", "b.txt")?;
 /// # Ok(())
 /// # }
 /// ```
@@ -278,7 +278,7 @@ pub fn symlink_file<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q)
 /// use std::os::windows::fs;
 ///
 /// # fn foo() -> std::io::Result<()> {
-/// try!(fs::symlink_file("a", "b"));
+/// fs::symlink_file("a", "b")?;
 /// # Ok(())
 /// # }
 /// ```