feat(statusline): remove arbitrary item group minwid limit

- with today's screens, the arbitrary 50 cells limit is no longer as
  ample as a few decades ago
- minwid is effectively constrained by the output buffer size anyway, so
  accidentally setting huge numbers introduces no noticeable lag
- restores some backwards compatibility to ui2 for the edge-case where
  the ruler width was set to a number > 50 with the item group syntax

src/nvim/statusline.c

@@ -1467,9 +1467,8 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, OptIndex op
       }
     }
 
-    // Bound the minimum width at 50.
     // Make the number negative to denote left alignment of the item
-    minwid = (minwid > 50 ? 50 : minwid) * (left_align ? -1 : 1);
+    minwid *= left_align ? -1 : 1;
 
     // Denotes the start of a new group
     if (*fmt_p == '(') {