Update Troubleshooting.md (#5794)

* Update Troubleshooting.md

I was trying to get jest debugging working and ran into issues. Switched to Node 9.7.1 and the issue went away, breakpoints were hit. Related: nodejs/node#7593

* Update Troubleshooting.md

Author: jcollum

docs/Troubleshooting.md

@@ -7,7 +7,8 @@ Uh oh, something went wrong? Use this guide to resolve issues with Jest.
 
 ### Tests are Failing and You Don't Know Why
 
-Try using the debugging support built into Node.
+Try using the debugging support built into Node. Note: This will only work in
+Node.js 8+.
 
 Place a `debugger;` statement in any of your tests, and then, in your project's
 directory, run: