add code comment to LinuxProcessTree's parser

Author: matthewbastien

lldb/tools/lldb-dap/src-ts/process-tree/platforms/linux-process-tree.ts

@@ -28,6 +28,7 @@ export class LinuxProcessTree extends BaseProcessTree {
         return;
       }
 
+      // ps will list "-" as the command if it does not know where the executable is located
       const command = line.slice(commandOffset, argumentsOffset).trim();
       if (command === "-") {
         return;