refactor(container): silence GCC 'final' warning

GCC now reports the following warning:

> linked-bump-allocator.h:39:7: error: Declaring type 'class
  quick_lint_js::Linked_Bump_Allocator<8>' final would enable
  devirtualization of 1 call [-Werror=suggest-final-types]

Heed GCC's warning by marking the class final.

src/quick-lint-js/container/linked-bump-allocator.h

@@ -36,7 +36,7 @@ namespace quick_lint_js {
 //
 // Internally, Linked_Bump_Allocator maintains a linked list of chunks.
 template <std::size_t alignment>
-class Linked_Bump_Allocator : public Memory_Resource {
+class Linked_Bump_Allocator final : public Memory_Resource {
  private:
   struct Chunk_Header;
   using Chunk = Flexible_Array<char, Chunk_Header>;