and delete a block of unreachable code

Test Plan:

```
python -m electroncash_plugins.fusion.tests
python -m electroncash.tests
./electrum-abc
```

Test Plan:

```
./electrum-abc
```

Open the receive tab, click the QR code, save to file.

Test Plan:
run unit tests, run electrum-abc

Test Plan:

run electrum-abc, test a few plugins (CashFusion, hw wallets)

Build the binaries, test the generated release files

Test Plan:

run electrum-abc

Build the binaries, test the generated release files

I didn't address the "import electroncash" instances in the previous commit.

There is a problem with pyinstaller on MacOS if the python lib and the package name are the same (case-insensitive).

Test Plan:

run from source, build the release files and test them

Note that there is no such package in the repository, but it is created at runtime when loading an external plugin.

TODO: create an external plugin compatible with the new package name to test this (the renaming of the packages is a breaking change for existing external electroncash plugins)

This fixes the case when secp256k1 is already cloned. Other packages are not affected because their git ref is a commit hash.