Upgrade coinmarketcap to 4.2.1

[fabaff]

Description:

Changelog: https://github.com/mrsmn/coinmarketcap/commits/master

Example entry for configuration.yaml (if applicable):

sensor:
  - platform: coinmarketcap

Checklist:

• The code change is tested and works locally.

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies have been added to the REQUIREMENTS variable ([example][ex-requir]).
• New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.