Fix nan_weak.h for V8 >= 14.2.194 (missing EmbedderDataTypeTag)

[gdavidkov]

Summary

• Commit fcc7b7d added V8 >= 14.2.194 compatibility guards to nan.h for GetAlignedPointerFromInternalField and SetAlignedPointerInInternalField (which now require an additional v8::kEmbedderDataTypeTagDefault tag parameter), but missed the same unguarded calls in nan_weak.h
• This causes build failures with Electron 41+ / V8 >= 14.2.194:

  error C2661: 'v8::Object::GetAlignedPointerFromInternalField': no overloaded function takes 1 arguments
  error C2660: 'v8::Object::SetAlignedPointerInInternalField': function does not take 2 arguments
  

• Applies the exact same preprocessor guard pattern from nan.h to the two call sites in nan_weak.h (inside the V8 >= 4.3 block, which is the only block compiled with V8 14.2+)

Test plan

• Build a native addon using NAN against Electron 41+ (V8 >= 14.2.194) and verify no compilation errors
• Verify existing builds against older V8 versions are unaffected (the # else branches preserve the original calls)

[kkoopa]

Thank you, I shall get this out right away.