fix: correct TOC anchors to match headings with mandatory suffix

Author: Quratulain-bilal

templates/spec-template.md

@@ -7,9 +7,9 @@
 
 ## Table of Contents
 
-- [User Scenarios & Testing](#user-scenarios--testing)
-- [Requirements](#requirements)
-- [Success Criteria](#success-criteria)
+- [User Scenarios & Testing](#user-scenarios--testing-mandatory)
+- [Requirements](#requirements-mandatory)
+- [Success Criteria](#success-criteria-mandatory)
 - [Assumptions](#assumptions)
 
 ## User Scenarios & Testing *(mandatory)*