EXAMPLES: update the basic-config-edge file for 2.8

- drop default ALPN values
- enable QUIC when the feature is built-in
diff --git a/examples/basic-config-edge.cfg b/examples/basic-config-edge.cfg
index 26aee68..8ee6bda 100644
--- a/examples/basic-config-edge.cfg
+++ b/examples/basic-config-edge.cfg
@@ -62,13 +62,20 @@
 	#  stats auth admin:mystats
 	#  stats admin if { src 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 127.0.0.0/8 }
 
-# First incoming public service. Supports HTTP/1.x and HTTP/2, using HSTS,
-# redirects clear to TLS. Uses a dedicated host name for the stats page.
+# First incoming public service. Supports HTTP/1.x, HTTP/2, and HTTP/3 over
+# QUIC when built in, uses HSTS, redirects clear to TLS. Uses a dedicated host
+# name for the stats page.
 frontend pub1
 	bind :80 name clear
-	bind :443 name secure ssl crt pub1.pem alpn h2,http/1.1
+	bind :443 name secure ssl crt pub1.pem
 	option socket-stats  # provide per-bind line stats
 
+.if feature(QUIC)
+	# indicate QUIC support for 25 hours
+	bind quic4@:443 name quic ssl crt pub1.pem allow-0rtt
+	http-response add-header alt-svc 'h3=":443"; ma=90000'
+.endif
+
 	# set HSTS for one year after all responses
 	http-after-response set-header Strict-Transport-Security "max-age=31536000"
 	http-request redirect scheme https code 301 if !{ ssl_fc }