REGTEST: fix a spurious "nbthread 4" in the connection test

Commit 26f6ae12c ("MAJOR: config: disable support for nbproc and nbthread
in parallel") revealed that there was accidently nbproc+nbthread in this
test while nbproc is the one expected. This likely is a leftover from a
previous attempt at reproducing the issue.
diff --git a/reg-tests/connection/b00000.vtc b/reg-tests/connection/b00000.vtc
index 415a670..f4206eb 100644
--- a/reg-tests/connection/b00000.vtc
+++ b/reg-tests/connection/b00000.vtc
@@ -22,7 +22,6 @@
 haproxy h1 -conf {
     global
         nbproc 4
-        nbthread 4
         tune.ssl.default-dh-param 2048
         stats bind-process 1
         log ${Slog_1_addr}:${Slog_1_port} len 2048 local0 debug err