Update single to double quotes inside config secrets.exs import code

[nandofarias]

Hello there 😀.

This change was introduced on the source code repo, and this PR intends to reflect the exact change in the book.

See: https://github.com/Cinderella-Man/hands-on-elixir-and-otp-cryptocurrency-trading-bot-source-code/commit/19ffb3676742a48814e8275843020927a827270a

[Cinderella-Man]

Hello Fernando,

Apologies for the late reply - I was prepping and travelling for the last few days,

I need to admit that you have impressive attention to detail :wink: Thank you very much for making this project better :heart:

Please feel free to raise any other things that you would find odd/wrong :wink:

[nandofarias]

Hi @Cinderella-Man, thank you for all your hard work on the book! I'm only enjoying the reading ❤️.

Have a nice day.