change: remove default issue title

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,7 +1,7 @@
 ---
 name: Bug report
 about: Create a report to help us improve
-title: BUG
+title: ''
 labels: Pending
 assignees: debugtalk
 ---

.github/ISSUE_TEMPLATE/bug_report_zh.md

@@ -1,7 +1,7 @@
 ---
 name: Bug 反馈（中文）
 about: 提交 bug 反馈
-title: BUG
+title: ''
 labels: Pending
 assignees: debugtalk
 ---

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,7 +1,7 @@
 ---
 name: Feature request
 about: Suggest an idea for this project
-title: FEATURE
+title: ''
 labels: Pending
 assignees: debugtalk
 ---

.github/ISSUE_TEMPLATE/feature_request_zh.md

@@ -1,7 +1,7 @@
 ---
 name: 需求反馈
 about: 期望新增或改进实现的需求
-title: FEATURE
+title: ''
 labels: Pending
 assignees: debugtalk
 ---