Remove feature label from feature request issue template (#25696)

We need a feature request process, so when a user submit a feature
proposal, it should not be marked as feature before it has been accept.

Author: lunny

.github/ISSUE_TEMPLATE/feature-request.yaml

@@ -1,6 +1,6 @@
 name: Feature Request
 description: Got an idea for a feature that Gitea doesn't have currently?  Submit your idea here!
-labels: ["kind/feature", "kind/proposal"]
+labels: ["kind/proposal"]
 body:
 - type: markdown
   attributes: