Add more snip sync

Author: Quinn-With-Two-Ns

core/src/main/java/io/temporal/samples/nexus/caller/EchoCallerWorkflowImpl.java

@@ -16,7 +16,7 @@
  *  express or implied. See the License for the specific language governing
  *  permissions and limitations under the License.
  */
-
+// @@@SNIPSTART samples-java-nexus-caller-echo-workflow
 package io.temporal.samples.nexus.caller;
 
 import io.temporal.samples.nexus.service.NexusService;
@@ -41,3 +41,4 @@ public String echo(String message) {
     return nexusService.echo(new NexusService.EchoInput(message)).getMessage();
   }
 }
+// @@@SNIPEND

core/src/main/java/io/temporal/samples/nexus/caller/HelloCallerWorkflowImpl.java

@@ -16,7 +16,7 @@
  *  express or implied. See the License for the specific language governing
  *  permissions and limitations under the License.
  */
-
+// @@@SNIPSTART samples-java-nexus-caller-hello-workflow
 package io.temporal.samples.nexus.caller;
 
 import io.temporal.samples.nexus.service.NexusService;
@@ -48,3 +48,4 @@ public String hello(String message, NexusService.Language language) {
     return handle.getResult().get().getMessage();
   }
 }
+// @@@SNIPEND