Bump version on issue template

Author: j-oliveras

.github/ISSUE_TEMPLATE/Bug_report.md

@@ -16,7 +16,7 @@ Please fill in the *entire* template below.
 -->
 
 <!-- Please try to reproduce the issue with `typescript@next`. It may have already been fixed. -->
-**TypeScript Version:**  3.3.0-dev.201xxxxx
+**TypeScript Version:**  3.4.0-dev.201xxxxx
 
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