Remove explicit dependency to Hipparchus in pom.xml
As Rugged depends on Orekit and Orekit depends on Hipparchus, there is no need to repeat the dependency to Hipparchus in pom.xml. For instance, the pom.xml of Rugged contains dependencies to hipparchus core, geometry and stat modules. But Rugged needs also the optim module. As this module is used by Orekit, there are no problems of compilation. So it is better to remove totally dependency to Hipparchus in the Rugged pom.xml, as there can be problems of version consistency between the one needed by Orekit and the one used in Rugged.