Improve template trigger/condition descriptions

[karwosts]

Proposed change

Two minor improvements to description rendering in expansion panel header for templates in automations:

1. The current description for template trigger is "When a template triggers". I think this can be improved, as this is somewhat of a circular definition and is not immediately clear what it means. (When does this trigger execute? When it triggers.).
   I propose the more exact description "When a template changes from false to true". I think this will be an improvement as there is sometimes some confusion around this trigger, with some users expecting it to trigger everytime the template evaluates to true.

2. Condition template currently has no description, and just displays "Template". This looks odd when juxtaposed with the other conditions, most/all of which use an imperitive sentence to describe the condition, such as "Test if... or "Confirm that....".
   I have added the sentence "Test if template renders a value equal to true", which matches how this condition is described in the official documentation.

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