Fix templates: "Category:X" is not a scoped label

.gitlab/issue_templates/Dogfooding.md

 <!--Lightweight issue template to encourage Dogfooding and educate team members about the importance of Dogfooding -->
 
-/label ~"dogfooding" ~"group::" ~"section::"  ~"Category::" 
+/label ~"dogfooding" ~"group::" ~"section::"  ~"Category:"
 
 ## Feature to Dogfood
 <!--Link to Description of feature (Documentation, Epic, Opportunity Canvas, etc.) -->

.gitlab/issue_templates/Feature proposal - detailed.md

@@ -37,7 +37,6 @@ Personas are described at https://about.gitlab.com/handbook/marketing/product-ma
 For example, "The user should be able to use the UI/API/.gitlab-ci.yml with GitLab to <perform a specific task>"
 https://about.gitlab.com/handbook/engineering/ux/ux-research-training/user-story-mapping/ -->
 
-
 ### Proposal
 
 <!-- How are we going to solve the problem? Try to include the user journey! https://about.gitlab.com/handbook/journeys/#user-journey -->

.gitlab/issue_templates/Fulfillment Group UX Issue.md

@@ -54,5 +54,5 @@ Personas are described at https://about.gitlab.com/handbook/marketing/product-ma
 
 
 
-/label ~"group::" ~"section::"  ~"Category::"  ~UX 
+/label ~"group::" ~"section::"  ~"Category:"  ~UX