Disable zipkin test in 3.0 (#289)

* disable zipkin test in 3.0

* disable zipkin run on 3.*
diff --git a/dubbo-samples-zipkin/case-versions.conf b/dubbo-samples-zipkin/case-versions.conf
index 96f7c4e..d666ab7 100644
--- a/dubbo-samples-zipkin/case-versions.conf
+++ b/dubbo-samples-zipkin/case-versions.conf
@@ -20,5 +20,5 @@
 # Supported component versions of the test case
 
 # Spring app
-dubbo.version=[ <2.7.8, >=2.7.9 ]
+dubbo.version=[ <2.7.8, >=2.7.9, !3.* ]
 spring.version=[ 4.*, 5.* ]