Upgrade Adafruit-DHT to 1.4.0 (fixes #15847)

[fabaff]

Description:

• Support for Pi 3B+

Related issue (if applicable): fixes #15847

Example entry for configuration.yaml (if applicable):

sensor:
  platform: dht
  sensor: DHT22
  pin: 23
  monitored_conditions:
    - temperature
    - humidity

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.

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

• New dependencies have been added to the REQUIREMENTS variable ([example][ex-requir]).
• New or updated dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.

[pvizeli]

Can we lock until after 0.83? Need some change for docker images

[pvizeli]

Need: home-assistant/docker#21

[balloob]

0.83.0b0 has been cut

[fabaff]

@pvizeli, merge it when you are ready.