provision: Update unsupported architecture logging messages.

We don't use zulip-devel@ anymore, and also add a comment that it's
probably not a huge project to support e.g. arm.

tools/lib/provision.py

@@ -110,7 +110,10 @@ elif platform.architecture()[0] == '32bit':
     arch = "i386"
 else:
     logging.critical("Only x86 is supported;"
-                     "ping zulip-devel@googlegroups.com if you want another architecture.")
+                     " ask on chat.zulip.org if you want another architecture.")
+    # Note: It's probably actually not hard to add additional
+    # architectures; the main problem is that we may not have
+    # tsearch_extras binaries compiled (and some testing is required).
     sys.exit(1)
 
 # Ideally we wouldn't need to install a dependency here, before we