[build] Remove deleted headers from BUILD.gn

Removes references to previously deleted headers:
src/sanitizer/lsan-page-allocator.h
src/base/atomicops_internals_portable.h
src/base/atomicops_internals_std.h

Bug: v8:7330
Change-Id: I8834d8041f50d4cd9402fc57490e8a6e0e7d5c76
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2851885
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74214}

BUILD.gn

@@ -2994,7 +2994,6 @@ v8_header_set("v8_internal_headers") {
     "src/runtime/runtime-utils.h",
     "src/runtime/runtime.h",
     "src/sanitizer/asan.h",
-    "src/sanitizer/lsan-page-allocator.h",
     "src/sanitizer/msan.h",
     "src/sanitizer/tsan.h",
     "src/snapshot/code-serializer.h",
@@ -4553,8 +4552,6 @@ v8_component("v8_libbase") {
     "src/base/atomic-utils.h",
     "src/base/atomicops.h",
     "src/base/atomicops_internals_atomicword_compat.h",
-    "src/base/atomicops_internals_portable.h",
-    "src/base/atomicops_internals_std.h",
     "src/base/base-export.h",
     "src/base/bit-field.h",
     "src/base/bits-iterator.h",