chore: fix feature template checklist to be for features, not bugs

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes 🚀 Feature: Add .only #194
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Quickly corrects the template.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (6108be1) to head (e13c44a).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #196   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           14        14           
  Lines          263       263           
  Branches        28        28           
=========================================
  Hits           263       263           

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