deps: update spring.version to v2.5.6 (#729)

* deps: update spring.version to v2.5.6

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Author: renovate-bot

vision/spring-framework/pom.xml

@@ -19,7 +19,7 @@ limitations under the License.
   <properties>
     <maven.compiler.target>1.8</maven.compiler.target>
     <maven.compiler.source>1.8</maven.compiler.source>
-    <spring.version>2.5.5</spring.version>
+    <spring.version>2.5.6</spring.version>
   </properties>
 
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