Cleanup stable-v0.5 branch

The kAFL [`stable-v0.5`](https://github.com/IntelLabs/kAFL/tree/stable-v0.5) branch was established to get a stable pinned version of kAFL for the ccc repo.

However, even if the ccc repo's [`requirements.yml`](https://github.com/intel/ccc-linux-guest-hardening/blob/master/deploy/requirements.yml#L5) refers to this branch, the variables defined in the branch's [`site.yml`](https://github.com/IntelLabs/kAFL/blob/stable-v0.5/deploy/site.yml#L17)
```YAML
- role: intellabs.kafl.fuzzer
tags:
- fuzzer
vars:
# branches maintained for this version
- fuzzer_revision: 'v0.5.1'
- qemu_revision: 'kafl-v0.5'
- examples_revision: 'v0.1'
# no maintained branch - try latest
# - libxdc_revision: 'ec596317'
# - capstone_revision: '0efa3cc5'
# - radamsa_revision: 'df651a67'
# - nyx_packer_revision: 'ef990c60'
```

Are actually overriden by the [`bkc`](https://github.com/intel/ccc-linux-guest-hardening/blob/master/deploy/roles/bkc/meta/main.yml) role from the ccc repo:

```YAML
dependencies:
- role: intellabs.kafl.fuzzer
tags:
- fuzzer
vars:
fuzzer_revision: kafl_tdx
qemu_revision: kafl_stable_tdx
libxdc_revision: kafl_stable_tdx
```

The changes brought by `kafl_tdx` branch on `kafl.fuzzer`:
https://github.com/IntelLabs/kafl.fuzzer/compare/v0.5.1...kafl_tdx

The changes brought by `kafl_stable_tdx` on `kafl.qemu`:
https://github.com/IntelLabs/kafl.qemu/compare/kafl-v0.5...kafl_stable_tdx

Start with deploy/site.yml on stable-v0.5 and compare its revision variables with deploy/roles/bkc/meta/main.yml in the ccc repository. Review the linked kafl.fuzzer and kafl.qemu comparisons to understand the branch differences. Done means the stable branch's pins and the ccc role overrides have an agreed, consistent purpose.

Written by the indexing model from the issue text.