fix: delete suggestion issues, use discussions

.github/ISSUE_TEMPLATE/suggest.yml

@@ -1,12 +0,0 @@
-name: Suggestion
-description: Suggest a feature to be added
-title: 'Suggestion: '
-labels: ['suggestion']
-body:
-  - type: textarea
-    id: suggest
-    attributes:
-      label: Suggestion
-      description: Be as descriptive as possible!
-      placeholder: What do you want in Zipline?
-      value: A suggestion