[docs] simplify bug report template (#3921)

* [docs] simplify bug report template

* Update .github/ISSUE_TEMPLATE/BUG_REPORT.md
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

.github/ISSUE_TEMPLATE/BUG_REPORT.md

@@ -3,65 +3,24 @@ name: Bug Report 🐞
 about: Something isn't working as expected? Here is the right place to report.
 ---
 
-<!--
-Please search your question on previous issues, Stack Overflow (https://stackoverflow.com/questions/tagged/lightgbm) or other search engines before you open a new one.
+## Description
+<!-- A clear description of the bug -->
 
-Also, for bugs and unexpected issues, please check the latest master branch first.
--->
-
-## How you are using LightGBM?
-
-<!-- 
-Choose one of the following components
-
-* R package
-* Python package
-* C++ library
-* Command Line Interface (CLI)
-* Java via SWIG
-* Other (please specify)
--->
-LightGBM component: 
+## Reproducible example
+<!-- Minimal code that exhibits this behavior -->
 
 ## Environment info
 
-<!-- Fill out each of the below. If something is not applicable, put 'N/A' or leave it blank -->
-
-Operating System:
-
-CPU/GPU model:
-
-C++ compiler version:
-
-CMake version:
-
-Java version:
-
-Python version:
-
-R version:
-
-Other:
-
-<!-- Please check the latest master branch first -->
 LightGBM version or commit hash:
 
-## Error message and / or logs
-
-<!-- Paste error log below (please avoid screenshots, use raw text) -->
-
+Command(s) you used to install LightGBM
 
-## Reproducible example(s)
+```shell
 
-<!--
-Paste examples code below (please avoid screenshots, use raw text).
+```
 
-If possible, try to provide a minimum working example that does not
-require access to proprietary data: https://stackoverflow.com/help/minimal-reproducible-example.
--->
+<!-- Put any additional environment information here -->
 
-## Steps to reproduce
 
-1.
-2.
-3.
+## Additional Comments
+<!-- What else should we know? -->