Fixed unit of measurement. #70121

[StephanU]

Proposed change

This PR fixes #70121 by adding the unit of measurement for "degree" and also fixes an issue when the unit of measurement reported by the edl21 meter is "0" (zero).

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)
• Deprecation (breaking change to happen in the future)
• 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 edl21 reports issue adding entities #70121

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.

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[probot-home-assistant]

Hey there @mtdcr, mind taking a look at this pull request as it has been labeled with an integration (edl21) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[frenck]

LGTM, Thanks @StephanU 👍