noproxy: fix build on systems without IPv6

Follow-up to ff2aaed9ba6f186feb57f89fc6854
Reported-by: Harry Sintonen
Closes #19860
diff --git a/lib/noproxy.c b/lib/noproxy.c
index e0d0877..86acf8b 100644
--- a/lib/noproxy.c
+++ b/lib/noproxy.c
@@ -211,8 +211,10 @@
     namelen = strlen(name);
     if(curlx_inet_pton(AF_INET, name, &address) == 1)
       type = TYPE_IPV4;
+#ifdef USE_IPV6
     else if(curlx_inet_pton(AF_INET6, name, &address) == 1)
       type = TYPE_IPV6;
+#endif
     else {
       /* ignore trailing dots in the hostname */
       if(name[namelen - 1] == '.')