Remove the Vector::append overload that takes a Vector

Source/core/css/RuleFeature.cpp

Index: Source/core/css/RuleFeature.cpp
diff --git a/Source/core/css/RuleFeature.cpp b/Source/core/css/RuleFeature.cpp
index 1395acf0e6f59aca9dfcef749802b97bc3626a39..b721dc252425a18fec844662a584576c6ad0ff86 100644
--- a/Source/core/css/RuleFeature.cpp
+++ b/Source/core/css/RuleFeature.cpp
@@ -248,8 +248,8 @@ void RuleFeatureSet::add(const RuleFeatureSet& other)
 
     m_metadata.add(other.m_metadata);
 
-    siblingRules.append(other.siblingRules);
-    uncommonAttributeRules.append(other.uncommonAttributeRules);
+    siblingRules.appendVector(other.siblingRules);
+    uncommonAttributeRules.appendVector(other.uncommonAttributeRules);
 }
 
 void RuleFeatureSet::clear()