doc: Update PR template

Author: iluwatar

PULL_REQUEST_TEMPLATE.md

@@ -1,14 +1,7 @@
-<!--
-Thank you for contributing to Java Design Patterns!
+# Pull Request Template
 
-If you're unsure where to start, please refer to the contributing doc:
+## What does this PR do?
 
-https://github.com/iluwatar/java-design-patterns/wiki/01.-How-to-contribute
+<!-- Provide a short description of what this pull request does. -->
 
-If you still have questions, please let us know via issues or [gitter](https://matrix.to/#/#iluwatar_java-design-patterns:gitter.im).
--->
-
-## What problem does this PR solve?
-
-<!-- Please describe the problem you're trying to solve. Uncomment the following line if this PR closes some issues -->
-<!-- Close #<issue number> -->
+<!-- Fixes #<issue-number> (if applicable) -->