Reword the feature_request issue template as enhancement (#3481)

.github/ISSUE_TEMPLATE/enhancement.md

@@ -0,0 +1,13 @@
+---
+name: Enhancement
+about: Suggest an improvement
+title: ''
+labels: C-enhancement
+assignees: ''
+---
+
+<!--
+Your enhancement may already be reported!
+Please search on the issue tracker before creating a new issue.
+If this is an idea for a feature, please open an "Idea" Discussion instead.
+-->

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,13 +0,0 @@
----
-name: Feature request
-about: Suggest a new feature or improvement
-title: ''
-labels: C-enhancement
-assignees: ''
----
-
-<!-- Your feature may already be reported!
-Please search on the issue tracker before creating one. -->
-
-#### Describe your feature request
-