chore: remote issue title prefix from template (#533)

* chore: remote issue title prefix from template

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

* change feature request's label name

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -1,8 +1,7 @@
 ---
 name: Bug report
 description: Is something not working? Help us fix it!
-title: "[Bug]: <Title>"
-labels: ["bug", "triage"]
+labels: [ "bug" ]
 body:
   - type: markdown
     attributes:

.github/ISSUE_TEMPLATE/enhancement.yml

@@ -1,7 +1,6 @@
 ---
 name: Enhancement
 description: Suggest an enhancement to existing functionality
-title: "[Enhancement]: <Title>"
 labels: [ "enhancement" ]
 body:
   - type: dropdown

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -1,8 +1,7 @@
 ---
 name: Feature request
 description: Suggest a new feature for GreptimeDB
-title: "[Feature]: <Feature name>"
-labels: [ "feature-request" ]
+labels: [ "feature request" ]
 body:
   - type: markdown
     id: info