Fix comment syntax (#224)

_This PR applies 1/3 suggestions from code quality [AI
findings](https://github.com/Cpp2Rust/cpp2rust/security/quality/ai-findings).
2 suggestions were skipped to avoid creating conflicts._

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

Author: nunoplopes

libcc2rs/src/io.rs

@@ -63,23 +63,23 @@ pub fn cerr() -> Ptr<std::fs::File> {
 /// # Safety
 ///
 /// The caller must ensure that the returned pointer is not used after the
-//  thread finishes.
+/// thread finishes.
 pub unsafe fn cin_unsafe() -> *mut std::fs::File {
     UNSAFE_STDIN.with(UnsafeCell::get)
 }
 
 /// # Safety
 ///
 /// The caller must ensure that the returned pointer is not used after the
-//  thread finishes.
+/// thread finishes.
 pub unsafe fn cout_unsafe() -> *mut std::fs::File {
     UNSAFE_STDOUT.with(UnsafeCell::get)
 }
 
 /// # Safety
 ///
 /// The caller must ensure that the returned pointer is not used after the
-//  thread finishes.
+/// thread finishes.
 pub unsafe fn cerr_unsafe() -> *mut std::fs::File {
     UNSAFE_STDERR.with(UnsafeCell::get)
 }