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

Remove unused code (4/4)

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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

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

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1 files changed, 0 insertions, 10 deletions

diff --git a/components/style/rule_tree/mod.rs b/components/style/rule_tree/mod.rs
index 34222103241..3b45035f46d 100644
--- a/components/style/rule_tree/mod.rs
+++ b/components/style/rule_tree/mod.rs
@@ -154,16 +154,6 @@ impl StyleSource {
         block.read_with(guard)
     }
 
-    /// Indicates if this StyleSource is a style rule.
-    pub fn is_rule(&self) -> bool {
-        self.0.is_first()
-    }
-
-    /// Indicates if this StyleSource is a PropertyDeclarationBlock.
-    pub fn is_declarations(&self) -> bool {
-        self.0.is_second()
-    }
-
     /// Returns the style rule if applicable, otherwise None.
     pub fn as_rule(&self) -> Option<ArcBorrow<Locked<StyleRule>>> {
         self.0.as_first()