[yaml2obj][obj2yaml][Object][test] - Improve testing of relocation types.

The intention was to remove the `Object/X86/yaml-elf-x86-rel-broken.yaml test`,
This test is at the wrong place.

`yaml-elf-x86-rel-broken.yaml` was introduced in
rG892c6c86ea25dc97668ff1f1b7bf1108e85fa5ec to check that
yaml2obj can use an arbitrary `Hex32` value as a relocation type.
We have tests that check the similar functionality.

I've improved them and removed the `yaml-elf-x86-rel-broken.yaml`

Differential revision: https://reviews.llvm.org/D75679