wrong value for ticker channel in crypto.com

[KamranBiglari]

The ask key is not "a" and it's "k" https://exchange-docs.crypto.com/spot/index.html#public-get-ticker

a: The price of the latest trade, null if there weren't any trades k: The current best ask price, null if there aren't any asks

Description of code - what bug does this fix / what feature does this add?

• [ ] - Tested
• [ ] - Changelog updated
• [ ] - Tests run and pass
• [ ] - Flake8 run and all errors/warnings resolved
• [ ] - Contributors file updated (optional)