This is the infamous seamfix mesh:
Its designed to hide the seams where the arms and head join the body since they are separate meshes. You can see these seams here which I have duplicated and highlighted in green:
Unfortunately, the seamfix mesh in game does not match the player body's skin material so the cure ends up being worse than the disease.
On PC this mesh is frequently hidden or replaced by another mesh via modding. I replaced the seamfix mesh with the doll cyberware decal mesh and the ugly grey harness goes away. If you are on console you can't do this because no mods but I am a strong advocate of a creation club system where CDPR curates and QA tests the best mods on say a quarterly basis and makes them available for console users as free DLC download packs.
Seamfix is one of those issues that annoyed me from day 1 and I have been playing with seamfix removers/replacers since late December.