regex: some minor polish

I think I already did a clean-up of this crate when I moved it to regex
1.9, so the polish here is very minor.

crates/regex/src/matcher.rs

@@ -831,9 +831,10 @@ impl RegexCaptures {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use grep_matcher::{LineMatchKind, Matcher};
 
+    use super::*;
+
     // Test that enabling word matches does the right thing and demonstrate
     // the difference between it and surrounding the regex in `\b`.
     #[test]