Fix jbang-example.java shebang line and dependency version

The first line was a bare '!' instead of the proper JBang shebang
'///usr/bin/env jbang'. Also updated the dependency version from
0.3.0-java.2 to the current 0.3.1-java.1-SNAPSHOT.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: brunoborges

jbang-example.java

@@ -1,5 +1,5 @@
-!
-//DEPS com.github:copilot-sdk-java:0.3.0-java.2
+///usr/bin/env jbang "$0" "$@" ; exit $?
+//DEPS com.github:copilot-sdk-java:0.3.1-java.1-SNAPSHOT
 import com.github.copilot.sdk.CopilotClient;
 import com.github.copilot.sdk.generated.AssistantMessageEvent;
 import com.github.copilot.sdk.generated.SessionUsageInfoEvent;