[JENKINS-75804] Webhook auto registration fail with PLUGIN implementation (#1066)

Remove hook secret when register webhook for PLUGIN implementation.

Author: nfalco79

src/main/java/com/cloudbees/jenkins/plugins/bitbucket/hooks/WebhookConfiguration.java

@@ -207,7 +207,6 @@ public BitbucketWebHook getHook(BitbucketSCMSource owner) {
                 hook.setDescription(description);
                 hook.setUrl(rootUrl + BitbucketSCMSourcePushHookReceiver.FULL_PATH);
                 hook.setCommittersToIgnore(committersToIgnore);
-                hook.setSecret(signatureSecret);
                 return hook;
             }
         }