.github: change issue checkboxes to dropdown

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -29,18 +29,19 @@ body:
       description: If so, what are those changes?
     validations:
       required: false
-  - type: checkboxes
+  - type: dropdown
     id: os
     attributes:
       label: OS
       description: What OS are you using? You may select more than one.
+      multiple: true
       options:
-        - label: Linux
+        - Linux
-        - label: macOS
+        - macOS
-        - label: Windows
+        - Windows
-        - label: iOS
+        - iOS
-        - label: Android
+        - Android
-        - label: Other
+        - Other
     validations:
       required: false
   - type: input