[skip ci] Remove predefined titles of issue template (#2768)

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -1,7 +1,6 @@
 name: Bug report/反馈 Bug
 description: Report errors or unexpected behavior./反馈错误或异常行为。
 labels: [bug]
-title: "[Bug] "
 body:
   - type: markdown
     attributes:

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -2,7 +2,6 @@
 name: Feature request/新特性请求
 description: Suggest an idea./提出建议
 labels: [enhancement]
-title: "[Feature Request] "
 body:
   - type: textarea
     attributes: