Add missing comma leading to unwanted str concat (#57758)

Ported from mono/mono#21197 

Co-authored-by: Ehsan Kia <contact@ehsankia.com>

Author: lambdageek

src/mono/mono/component/debugger-agent.c

@@ -9808,7 +9808,7 @@ static const char* vm_cmds_str [] = {
 	"INVOKE_METHOD",
 	"SET_PROTOCOL_VERSION",
 	"ABORT_INVOKE",
-	"SET_KEEPALIVE"
+	"SET_KEEPALIVE",
 	"GET_TYPES_FOR_SOURCE_FILE",
 	"GET_TYPES",
 	"INVOKE_METHODS",