Fix update job

[runleonarun]

Closes #69

Problem

The API documentation for updating jobs was inaccurate and made it hard for users to make simple changes to their jobs:

• "Try It" feature is broken - The interactive testing tool in the docs required users to fill out 13+ fields just to change one thing (like a job name)
• Confusing requirements - The docs said many fields were "required" when they actually weren't
• Doesn't match reality - The documentation didn't reflect how the API actually works

Fixes

Created a new schema HumanReadableJobDefinitionUpdateRequest and updated the Update Job endpoint to reference it, keeping the original create schema unchanged.

• Created accurate documentation for updates
• Made it clear that only 4 fields are truly required: account ID, project ID, environment ID, and job name
• All other fields (like schedule, commands, settings) are now correctly marked as optional
• Fixed the "Try It" feature
• Users can now test simple updates directly in the docs without filling out unnecessary fields
  Example: To change just a job's name, you only need to provide the 4 required fields plus the new name
• Documented flexible behavior. Made it clear that you can include extra information (like the job ID or read-only fields) and the API will simply ignore it
  • This is helpful because users can modify and send back the full job details they get from a "Get Job" request
• Better examples: Added realistic examples showing common update scenarios
• Improved descriptions to explain what each field does

Hopefully users will be able to update their jobs with accurate documentation that matches how the API actually works. Simple changes (like updating a job name or schedule) no longer require understanding or providing a dozen unrelated fields.

[runleonarun]

I tested the 4 required fields.

[runleonarun]

Closing to change in code source.