Auto merge of #14796 - jlevesy:jl-match-to-if-let, r=Wafflespeanut

replace match by if let statements if possible

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Hi there,

This PR replaces `match` statements by `if let` when possible.

Thanks for reviewing

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #14788

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because this PR is a code cleanup patch.

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components/style/str.rs

@@ -150,9 +150,8 @@ pub fn str_join<I, T>(strs: I, join: &str) -> String
 /// Like AsciiExt::to_ascii_lowercase, but avoids allocating when the input is already lower-case.
 pub fn cow_into_ascii_lowercase<'a, S: Into<Cow<'a, str>>>(s: S) -> Cow<'a, str> {
     let mut cow = s.into();
-    match cow.bytes().position(|byte| byte >= b'A' && byte <= b'Z') {
-        Some(first_uppercase) => cow.to_mut()[first_uppercase..].make_ascii_lowercase(),
-        None => {}
+    if let Some(first_uppercase) = cow.bytes().position(|byte| byte >= b'A' && byte <= b'Z') {
+        cow.to_mut()[first_uppercase..].make_ascii_lowercase();
     }
     cow
 }