[cxx-interop] NFC: rename initializer parameter

Author: egorzhdan

stdlib/public/Cxx/CxxConvertibleToCollection.swift

@@ -45,11 +45,11 @@ extension RangeReplaceableCollection {
   ///   container when each element is copied in O(1). Note that this might not
   ///   be true for certain C++ types, e.g. those with a custom copy
   ///   constructor that performs additional logic.
-  public init<C: CxxConvertibleToCollection>(_ c: C)
+  public init<C: CxxConvertibleToCollection>(_ elements: C)
     where C.RawIterator.Pointee == Element {
 
     self.init()
-    c.forEach { self.append($0) }
+    elements.forEach { self.append($0) }
   }
 }
 
@@ -62,10 +62,10 @@ extension SetAlgebra {
   ///   container when each element is copied in O(1). Note that this might not
   ///   be true for certain C++ types, e.g. those with a custom copy
   ///   constructor that performs additional logic.
-  public init<C: CxxConvertibleToCollection>(_ c: C)
+  public init<C: CxxConvertibleToCollection>(_ elements: C)
     where C.RawIterator.Pointee == Element {
 
     self.init()
-    c.forEach { self.insert($0) }
+    elements.forEach { self.insert($0) }
   }
 }