docs: Update API Endpoints params

[albertorm95]

what

This pull request updates the API documentation to clarify and improve the parameter definitions for the /api/plan and /api/apply endpoints. The main changes are the introduction of the Projects parameter, clarification of the Paths parameter, and a note about their usage requirements.

API parameter improvements:

• Added a Projects parameter ([]string) as an optional way to specify project names for both the /api/plan and /api/apply endpoints.
• Changed the Paths parameter to be optional and accept multiple values ([]Path) instead of a single required value.
• Added a documentation note stating that at least one of Projects or Paths must be specified for these endpoints.

why

Docs were out-of-date

tests

n/a

references

• atlantis/server/controllers/api_controller.go

  Lines 47 to 57 in 8fd24e7

  	type APIRequest struct {
  	Repository string `validate:"required"`
  	Ref string `validate:"required"`
  	Type string `validate:"required"`
  	PR int
  	Projects []string
  	Paths []struct {
  	Directory string
  	Workspace string
  	}
  	}