tracing add zipkin dep default

[songxiaosheng]

What is the purpose of the change?

when i use dubbo-tracing-brave-zipkin-spring-boot-starter start tracing ,it will cause a error ClassNotFoundException: zipkin2.codec.BytesEncoder， so i think add zipkin dep default

<dependency>
        <groupId>org.apache.dubbo</groupId>
        <artifactId>dubbo-tracing-brave-zipkin-spring-boot-starter</artifactId>
      </dependency>

Caused by: java.lang.ClassNotFoundException: zipkin2.codec.BytesEncoder
	at jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[?:?]
	at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) ~[?:?]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:528) ~[?:?]
	at java.lang.Class.forName0(Native Method) ~[?:?]
	at java.lang.Class.forName(Class.java:578) ~[?:?]
	at java.lang.Class.forName(Class.java:557) ~[?:?]
	at org.springframework.boot.autoconfigure.condition.FilteringSpringBootCondition.resolve(FilteringSpringBootCondition.java:108) ~[spring-boot-autoconfigure-2.7.8.jar:2.7.8]
	at org.springframework.boot.autoconfigure.condition.OnBeanCondition$Spec.getReturnType(OnBeanCondition.java:532) ~[spring-boot-autoconfigure-2.7.8.jar:2.7.8]
	at org.springframework.boot.autoconfigure.condition.OnBeanCondition$Spec.deducedBeanTypeForBeanMethod(OnBeanCondition.java:520) ~[spring-boot-autoconfigure-2.7.8.jar:2.7.8]
	at org.springframework.boot.autoconfigure.condition.OnBeanCondition$Spec.deducedBeanType(OnBeanCondition.java:513) ~[spring-boot-autoconfigure-2.7.8.jar:2.7.8]
	at org.springframework.boot.autoconfigure.condition.OnBeanCondition$Spec.<init>(OnBeanCondition.java:436) ~[spring-boot-autoconfigure-2.7.8.jar:2.7.8]
	at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchOutcome(OnBeanCondition.java:154) ~[spring-boot-autoconfigure-2.7.8.jar:2.7.8]
	at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:47) ~[spring-boot-autoconfigure-2.7.8.jar:2.7.8]
	... 16 more

Checklist

• Make sure there is a GitHub_issue field for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Make sure gitHub actions can pass. Why the workflow is failing and how to fix it?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.78%. Comparing base (cad36ee) to head (27f8250).

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #15231      +/-   ##
============================================
+ Coverage     60.76%   60.78%   +0.01%     
- Complexity    10892    10896       +4     
============================================
  Files          1885     1885              
  Lines         86072    86072              
  Branches      12893    12893              
============================================
+ Hits          52305    52319      +14     
+ Misses        28317    28310       -7     
+ Partials       5450     5443       -7     

Flag	Coverage Δ
integration-tests	33.19% <ø> (ø)
samples-tests	29.23% <ø> (+0.03%)	⬆️
unit-tests	58.91% <ø> (+0.02%)	⬆️

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