Revert "Bump timeout for initial serial read (30s->60s)"

Reverting as this is only needed on very slow machines, and it didn't
really fix the problem, as it just fails on another line due to a
timeout.

This reverts commit ad830608.

build-host.sh

@@ -103,7 +103,7 @@ function main() {
   start_qemu
 
   # Login
-  expect "archiso login:" 60
+  expect "archiso login:"
   send "root\n"
   expect "# "