Need `electrum_tls` set to False

I am posting here as issue seems to affect all platforms tested (iOS; Mac OS), and configuration option causing problem on all platforms AFAICT is in this repository at: https://github.com/Blockstream/gdk/blob/fb8a9a0d0600212280c036a1a21e028202b5a3ad/src/network_parameters.cpp#L331

## Description of Problem

I can't connect to a personal electrum server, which causes all sorts of unexpected failure behaviours across all platforms when creating or restoring wallets

## Cause of problem

I believe this is because Green/GDK always forces Electrum TLS to be true, and I am running non-TLS only on port 50001.

## Logs

### GDK

Note `electrum_url` is `electrs.local:50001`, and `electrum_tls` is `Bool(true)`.

```
[2022-04-16 13:07:46.813813] [gdk:debug] 46.813 INFO - create_session Object({"address_explorer_url": String("https://blockstream.info/address/"), "bech32_prefix": String("bc"), "bip21_prefix": String("bitcoin"), "cert_expiry_threshold": Number(1), "csv_buckets": Array([]), "development": Bool(false), "electrum_onion_url": String("omitted.onion:110"), "electrum_tls": Bool(true), "electrum_url": String("electrs.local:50001"), "liquid": Bool(false), "mainnet": Bool(true), "max_reorg_blocks": Number(144), "name": String("Bitcoin (Electrum)"), "network": String("electrum-mainnet"), "p2pkh_version": Number(0), "p2sh_version": Number(5), "pin_server_onion_url": ...
```

### Electrs

```
[2022-04-16T17:17:08.200Z WARN electrs::server] InvalidData on first line may indicate client attempted to connect using SSL when server expects unencrypted communication.
[2022-04-16T17:17:08.200Z WARN electrs::thread] recv_loop thread failed: 0: recv failed
[2022-04-16T17:17:08.200Z WARN electrs::thread] because: stream did not contain valid UTF-8
```

## Setup details

Green Wallet, latest version from official channels on iOS and Mac OS

Electrs, git commit 1b4cc1ec0fd51caeea92da9d959a00805a4810a4 (latest)

Green and Electrs running on private network, not publicly exposed (hence no TLS)

Bitcoin mainnet