edje edje_embryo: use strncpy().

This change is not meaningful but avoids an annoying coverity detection.

src/lib/edje/edje_embryo.c

@@ -1553,10 +1553,9 @@ _edje_embryo_fn_get_text(Embryo_Program *ep, Embryo_Cell *params)
           }
         else
           {
-             char *ss;
-
-             ss = alloca(strlen(s) + 1);
-             strcpy(ss, s);
+             int size = strlen(s) + 1;
+             char *ss = alloca(size);
+             strncpy(ss, s, size);
              ss[params[3] - 1] = 0;
              SETSTR(ss, params[2]);
           }