Auto merge of #23532 - est31:unused_code_removal_4, r=emilio

Remove unused code (4/4)

<!-- Please describe your changes on the following line: -->

Fourth and final PR in a series of PRs to remove unused/dead code from servo, powered by an (upcoming) tool of mine. Please take a look and tell me if you want to keep something.

* First PR: #23477
* Second PR: #23498
* Third PR: #23499

Shortstat of the combined PR series:
```
47 files changed, 7 insertions(+), 805 deletions(-)
```

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors

<!-- Either: -->
- [ ] There are tests for these changes OR
- [x] These changes do not require tests because they only remove dead code

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23532)
<!-- Reviewable:end -->

components/style/bloom.rs

@@ -194,11 +194,6 @@ impl<E: TElement> StyleBloom<E> {
         Some(popped_element)
     }
 
-    /// Returns true if the bloom filter is empty.
-    pub fn is_empty(&self) -> bool {
-        self.elements.is_empty()
-    }
-
     /// Returns the DOM depth of elements that can be correctly
     /// matched against the bloom filter (that is, the number of
     /// elements in our list).