README: Don't linkify text that is itself a URL

Markdown processing does this for us.

Change-Id: I1e77584c41b17ec43ceb6280a95876f2cb943a4a
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/README.md b/README.md
index 312ce66..62db3c3 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@
 
 ## Contact
 
-- Mail: openbmc@lists.ozlabs.org [https://lists.ozlabs.org/listinfo/openbmc](https://lists.ozlabs.org/listinfo/openbmc)
+- Mail: openbmc@lists.ozlabs.org https://lists.ozlabs.org/listinfo/openbmc
 - Discord: https://discord.gg/69Km47zH98
 - IRC: #openbmc on freenode.net