[cleanup] Delete old pointer compression comment

Bug: v8:7703
Change-Id: I06c9e04b1c8ab3c6461468db2f7a035a12ccf7d0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2230522
Auto-Submit: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68170}

BUILD.gn

@@ -272,7 +272,6 @@ if (v8_enable_snapshot_native_code_counters == "") {
   v8_enable_snapshot_native_code_counters = v8_enable_debugging_features
 }
 if (v8_enable_pointer_compression == "") {
-  # TODO(v8:v7703): temporarily enable pointer compression on arm64 and on x64
   v8_enable_pointer_compression =
       v8_current_cpu == "arm64" || v8_current_cpu == "x64"
 }