quiet a warning compiling sys/share/uudecode in recent compiler

../sys/share/uudecode.c: In function ‘main’:
../sys/share/uudecode.c:131:32: warning: format ‘%o’ expects argument of type ‘unsigned int *’, but argument 3 has type ‘int *’ [-Wformat=]
  131 |     (void) sscanf(buf, "begin %o %s", &mode, dest);
      |                               ~^      ~~~~~
      |                                |      |
      |                                |      int *
      |                                unsigned int *
      |                               %o

sys/share/uudecode.c

@@ -99,7 +99,7 @@ int
 main(int argc, char **argv)
 {
     FILE *in, *out;
-    int mode;
+    unsigned int mode;
     char dest[128];
     char buf[80];