bridge tests: re-enable span test

The root cause of the intermittent span test failures has been
identified as a race between sending the packet and starting the bpf
capture.
This is now resolved, so the test can be re-enabled.

PR:		260461
MFC after:	1 week
Sponsored by:	Rubicon Communications, LLC ("Netgate")

tests/sys/net/if_bridge_test.sh

@@ -273,13 +273,8 @@ span_head()
 
 span_body()
 {
-	set -x
 	vnet_init
 
-	if [ "$(atf_config_get ci false)" = "true" ]; then
-		atf_skip "https://bugs.freebsd.org/260461"
-	fi
-
 	epair=$(vnet_mkepair)
 	epair_span=$(vnet_mkepair)
 	bridge=$(vnet_mkbridge)