Fix the display of number of running tasks

This was broken by a logic change in 72235d8.

Fixes: htop-dev#1369

linux/LinuxMachine.c

@@ -489,8 +489,7 @@ static void LinuxMachine_scanCPUTime(LinuxMachine* this) {
    char buffer[PROC_LINE_LENGTH + 1];
    while (fgets(buffer, sizeof(buffer), file)) {
       if (String_startsWith(buffer, "procs_running")) {
-         ProcessTable* pt = (ProcessTable*) super->processTable;
-         pt->runningTasks = strtoul(buffer + strlen("procs_running"), NULL, 10);
+         this->runningTasks = strtoul(buffer + strlen("procs_running"), NULL, 10);
          break;
       }
    }