fix(workflow): remove execute policy restriction for template delta

[Cynthia-0203]

What this PR does / Why we need it:

Allows template-bound workflows to customize each Job’s execution policy through Delta patches.

Previously, the backend enforced the template’s execute_policy, preventing workflow instances from changing or removing it.

What is changed and how it works?

• Removed the backend validation that required Job execution policies to match the workflow template.
• Delta patches can now directly modify execute_policy or replace a Job with a different execution policy.
• Other template binding, JSON Patch, and workflow validation logic remains unchanged.

Does this PR introduce a user-facing change?

• API change
• database schema change
• upgrade assistant change
• change in non-functional attributes such as efficiency or availability
• fix of a previous issue

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This change is