[clang] [libunwind] [llvm] Replace documentation mentions of IRC with Discord (PR #114276)

[Joshua Cranmer via cfe-commits]

================
@@ -388,27 +384,18 @@ Guidance for office hours hosts
   from the list above.
 
 
-.. _IRC:
-
-IRC
----
+Discord
----------------
jcranmer-intel wrote:

You've removed the thing that lets you link to this section, if I'm recalling my RST correctly.

https://github.com/llvm/llvm-project/pull/114276