Update issue templates

Former-commit-id: c1c34440488b8eda0e6b6be093ed6dd6fbd8287d

.github/ISSUE_TEMPLATE/-bug--bug-report.md

----
-name: ":bug: Bug report"
-about: Create a bug report to help us improve Milvus
-title: "[BUG]"
-labels: ''
-assignees: ''
-
----
-
-**Describe the bug**
-A clear and concise description of what the bug is.
-
-**Steps/Code to reproduce behavior**
-Follow this [guide](http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) to craft a minimal bug report. This helps us reproduce the issue you're having and resolve the issue more quickly.
-
-**Expected behavior**
-A clear and concise description of what you expected to happen.
-
-**Environment details**
-- Hardware/Softward conditions (OS, CPU, GPU, Memory)
-- Method of installation (Docker, or from source)
-- Milvus version (v0.3.1, or v0.4.0)
-- Milvus configuration (Settings you made in `server_config.yaml`)
-
-**Screenshots**
-If applicable, add screenshots to help explain your problem.
-
-**Additional context**
-Add any other context about the problem here.

.github/ISSUE_TEMPLATE/bug_report.md

 ---
 name: Bug report
 about: Create a bug report to help us improve Milvus
-title: ":bug:[BUG]"
+title: ":bug: [BUG]"
 labels: ''
 assignees: ''