Revert "Enable Dart compressed pointers for 64-bit mobile targets (#27975)"

This reverts commit d856fc3.

Author: zanderso

tools/gn

@@ -380,10 +380,6 @@ def to_gn_args(args):
     # on Android.
     gn_args['bssl_use_clang_integrated_as'] = True
 
-    # Enable pointer compression on 64-bit mobile targets.
-    if args.target_os in ['android', 'ios'] and gn_args['target_cpu'] in ['x64' , 'arm64']:
-      gn_args['dart_use_compressed_pointers'] = True
-
     return gn_args
 
 def parse_args(args):