Indent: improper indent following a comma

Filing a bug? Have you already tried updating `vim-elixir`? For indentation/highlighting bugs, please use the following template:

# Actual

```ex
config :logger,
level: (if level = System.get_env("LOG_LEVEL"), do: String.to_atom(level), else: :warn),
protocol_version: :"tlsv1.2"
```

# Expected

```ex
config :logger,
level: (if level = System.get_env("LOG_LEVEL"), do: String.to_atom(level), else: :warn),
protocol_version: :"tlsv1.2"
```