Bump dubbo in /sofa-tracer-plugins/sofa-tracer-dubbo-common-plugin (#481)

Bumps [dubbo](https://github.com/apache/incubator-dubbo) from 2.6.2 to 2.6.12.

Author: dependabot[bot]

sofa-tracer-plugins/sofa-tracer-dubbo-common-plugin/pom.xml

@@ -16,7 +16,7 @@
         <dependency>
             <groupId>com.alibaba</groupId>
             <artifactId>dubbo</artifactId>
-            <version>2.6.2</version>
+            <version>2.6.12</version>
             <scope>provided</scope>
         </dependency>