fix hidepid mount detection

kernel >= 5.8 now translates mode "1" to "noaccess" and mode "2" to "invisible", which breaks
Firejail's hidepid detection

src/lib/common.c

@@ -277,7 +277,7 @@ int pid_hidepid(void) {
  if (strstr(buf, "proc /proc proc")) {
  fclose(fp);
  // check hidepid
- if (strstr(buf, "hidepid=2") || strstr(buf, "hidepid=1"))
+ if (strstr(buf, "hidepid="))
  return 1;
  return 0;
  }