drop wagon-ssh extension

This was required for the sftp upload to a custom FTP server, which has been
removed from the deploy process.

(cherry picked from commit 707ad27)

Author: mtf90

pom.xml

@@ -410,14 +410,6 @@ limitations under the License.
                 </executions>
             </plugin>
         </plugins>
-
-        <extensions>
-            <extension>
-                <groupId>org.apache.maven.wagon</groupId>
-                <artifactId>wagon-ssh</artifactId>
-                <version>2.6</version>
-            </extension>
-        </extensions>
     </build>
 
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