Remove extraneous checkboxes from issue template

Fixes junit-team#657.

.github/ISSUE_TEMPLATE.md

@@ -3,17 +3,17 @@
 _Replace the following bullet points with your issue description,
 after answering yourself: **"What kind of issue is this?"**_
 
-- [ ] **Question.** This issue tracker is not the place for questions.
+- ( ) **Question.** This issue tracker is not the place for questions.
 If you want to ask how to do something, or to understand why
 something isn't working the way you expect it to, use Stack Overflow.
 https://stackoverflow.com/questions/tagged/junit5
 
-- [ ] **Bug report.** Please provide us the version of JUnit 5 you are
+- ( ) **Bug report.** Please provide us the version of JUnit 5 you are
 using and, if possible, a failing unit test with your bug report. Don't
 forget to describe the rationale for this issue (e.g. expected vs.
 actual behavior).
 
-- [ ] **Feature request.** Start by telling us what problem you’re trying
+- ( ) **Feature request.** Start by telling us what problem you’re trying
 to solve. Often a solution already exists! Please, don’t send pull requests
 to implement new features without first getting our support.