Make single_char_pattern clippy happy

Signed-off-by: hi-rustin <rustin.liu@gmail.com>

Author: 0xPoe

src/utils/utils.rs

@@ -557,7 +557,7 @@ pub(crate) fn toolchain_sort<T: AsRef<str>>(v: &mut Vec<T>) {
         } else if s.starts_with("nightly") {
             special_version(2, s)
         } else {
-            Version::parse(&s.replace("_", "-")).unwrap_or_else(|_| special_version(3, s))
+            Version::parse(&s.replace('_', "-")).unwrap_or_else(|_| special_version(3, s))
         }
     }
 

tests/mock/clitools.rs

@@ -463,7 +463,7 @@ fn print_indented(heading: &str, text: &str) {
         "{} ({} lines):\n    {}",
         heading,
         lines,
-        text.replace("\n", "\n    ")
+        text.replace('\n', "\n    ")
     );
 }