use released powsybl-core version

Signed-off-by: Nicolas Rol <[email protected]>

Author: rolnico

pom.xml

@@ -77,7 +77,7 @@
         <mockito.version>5.12.0</mockito.version>
         <slf4j.version>2.0.13</slf4j.version>
 
-        <powsyblcore.version>6.6.0-RC1</powsyblcore.version>
+        <powsyblcore.version>6.6.0</powsyblcore.version>
 
         <!-- Parameters used to generate the javadoc for groovy and java classes.
              See the pom file in powsybl-parent for more explanations. -->