Reword action descriptions for better translations in Teslemetry

[NoRi2909]

Proposed change

Currently only one of the action descriptions in the Teslemetry integration uses the descriptive form of third person plural which can cause wrong and misleading translations.

This commit changes the remaining descriptions to adopt the same language and changes "the" to "a" as the actual action target (vehicle or energy site) is defined later, below that in the UI.

In addition the description of the set_scheduled_departure action is updated to better explain what the options are.

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 #
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[home-assistant]

Hey there @Bre77, mind taking a look at this pull request as it has been labeled with an integration (teslemetry) you are listed as a code owner for? Thanks!

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