Updates link to reprex how-to in issues template (tidyverse#2385)

Closes tidyverse#2362

ISSUE_TEMPLATE.md

@@ -1,6 +1,6 @@
 Please briefly describe your problem and what output you expect. If you have a question, please don't use this form, but instead ask on the mailing list <https://groups.google.com/forum/#!forum/ggplot2> or stackoverflow <http://stackoverflow.com>.
 
-Please include a minimal reprex. The goal of a reprex is to make it as easy as possible for me to recreate your problem so that I can fix it. If you've never heard of a reprex before, start by reading <https://github.com/jennybc/reprex#what-is-a-reprex>, and follow the advice further down the page. Do NOT include session info unless it's explicitly asked for, or you've used `reprex::reprex(..., si = TRUE)` to hide it away.  
+Please include a minimal reprex. The goal of a reprex is to make it as easy as possible for me to recreate your problem so that I can fix it. If you've never heard of a reprex before, start by reading <https://www.tidyverse.org/help/#reprex>, and follow the advice further down the page. Do NOT include session info unless it's explicitly asked for, or you've used `reprex::reprex(..., si = TRUE)` to hide it away.  
 
 Delete these instructions once you have read them.