hh_client --remove-dead-fixmes removes ALL fixmes

**Describe the bug**
Instead of only removing dead fixmes (which don't produce a type error when removed) this command now removes all of them.

**Standalone code, or other way to reproduce the problem**
```
$ git clone https://github.com/hhvm/hhast.git
$ cd hhast
$ composer install
$ docker run -it -v $(pwd):/hhast -w /hhast hhvm/hhvm:4.153-latest bash
$ hh_client --no-load
No errors!
$ hh_client --remove-dead-fixmes
$ hh_client
...
744 errors found.
```

**Expected behavior**

Only fixmes which can be removed without introducing typechecker errors are removed.

**Actual behavior**

Seemingly all fixmes are removed, introducing typechecker errors.

**Environment**
- Operating system
Ubuntu 18.04
- Installation method
hhvm/hhvm on dockerhub
- HHVM Version
```
HipHop VM 4.153.0 (rel) (non-lowptr)
Compiler: 1647458518_157060578
Repo schema: 534e885b23eb8788358662b280cabd6799199f99
```