Update bug_report.yml (#906)

* Update bug_report.yml

Bugs do not always have tracebacks associated, so this field should be optional

* Update .github/ISSUE_TEMPLATE/bug_report.yml

Author: bendichter

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -35,9 +35,7 @@ body:
         Please copy and paste the full traceback produced by the error.
 
         This section will be automatically formatted into code, so no need for backticks.
-      render: shell
-    validations:
-      required: true
+      render: pytb
   - type: dropdown
     id: os
     attributes: