DSMR: Remove Gas derivative sensor

[frenck]

Breaking change

The Hourly Gas Consumption sensor has been removed from the DSMR integration.
This sensor was calculated and it is not an actual datapoint from the energy meter.

If you are looking for a replacement, you can use the Derivative integration to re-create the hourly (or any other timeframe)
sensor based on the total Gas consumption sensor.

Proposed change

This PR removes the hourly gas consumption sensor from the DSMR integration, as it was a calculated/virtual sensor that doesn't originate from the device/service the integration is connected to.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

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

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

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To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[probot-home-assistant]

Hey there @RobBie1221, mind taking a look at this pull request as its been labeled with an integration (dsmr) you are listed as a codeowner for? Thanks!
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