Use protobuf provided by ports

Index: Ghidra/Test/DebuggerIntegrationTest/src/test.slow/java/agent/drgn/rmi/DrgnConnectorsTest.java
--- Ghidra/Test/DebuggerIntegrationTest/src/test.slow/java/agent/drgn/rmi/DrgnConnectorsTest.java.orig
+++ Ghidra/Test/DebuggerIntegrationTest/src/test.slow/java/agent/drgn/rmi/DrgnConnectorsTest.java
@@ -54,7 +54,7 @@ public class DrgnConnectorsTest extends AbstractRmiCon
 		// Make sure system doesn't cause path failures to pass
 		unpip("ghidradrgn", "ghidratrace");
 		// Ensure a compatible version of protobuf
-		pip("protobuf==6.31.0");
+		pip("protobuf==${PROTOBUF_VER}");
 	}
 
 	@Test
