Change help link in statistics pickers in energy dashboard

[karwosts]

Proposed change

Change the "why is my entity not listed" help link for statistics pickers in the energy dashboard to a specific energy faq page detailing reasons why statistics may not be selectable for energy dashboard. This question comes up very frequently from users, and I think this page may be more helpful than the existing generic statistics help page, which does not really explain much detail about how to resolve the issue.

Old help link: https://www.home-assistant.io/more-info/statistics/
New help link: https://www.home-assistant.io/docs/energy/faq/#troubleshooting-missing-entities

Type of change

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

Example configuration

Additional information

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

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• 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