Update repo readme to remove reddit suggestion

Remove the link to reddit from the EGSnrc top-level readme, to focus
community exchanges in EGSnrc discussions. We would have to update the
info on the [webpage](https://nrc-cnrc.github.io/EGSnrc/) as well (on
the `gh-pages` branch).

README.md

@@ -80,8 +80,7 @@ for more details on how to download and configure EGSnrc.
 
 ## Support
 
-For technical support, consider the
-[EGSnrc reddit community](https://www.reddit.com/r/EGSnrc), the EGSnrc
+For technical support, consider the EGSnrc
 [Discussions](https://github.com/nrc-cnrc/EGSnrc/discussions), or
 [contact us](https://nrc.canada.ca/en/research-development/products-services/software-applications/egsnrc-software-tool-model-radiation-transport).