Remove `DEFAULT_` from `DEFAULT_MAJOR_GC_INC_RATIO`; ref #3998

Because unlike other GC ratio constants, it's not a default value.

src/gc.c

@@ -344,7 +344,7 @@ add_heap(mrb_state *mrb, mrb_gc *gc)
 
 #define DEFAULT_GC_INTERVAL_RATIO 200
 #define DEFAULT_GC_STEP_RATIO 200
-#define DEFAULT_MAJOR_GC_INC_RATIO 200
+#define MAJOR_GC_INC_RATIO 200
 #define is_generational(gc) ((gc)->generational)
 #define is_major_gc(gc) (is_generational(gc) && (gc)->full)
 #define is_minor_gc(gc) (is_generational(gc) && !(gc)->full)
@@ -1209,7 +1209,7 @@ mrb_incremental_gc(mrb_state *mrb)
     }
 
     if (is_major_gc(gc)) {
-      gc->majorgc_old_threshold = gc->live_after_mark/100 * DEFAULT_MAJOR_GC_INC_RATIO;
+      gc->majorgc_old_threshold = gc->live_after_mark/100 * MAJOR_GC_INC_RATIO;
       gc->full = FALSE;
     }
     else if (is_minor_gc(gc)) {
@@ -1248,7 +1248,7 @@ mrb_full_gc(mrb_state *mrb)
   gc->threshold = (gc->live_after_mark/100) * gc->interval_ratio;
 
   if (is_generational(gc)) {
-    gc->majorgc_old_threshold = gc->live_after_mark/100 * DEFAULT_MAJOR_GC_INC_RATIO;
+    gc->majorgc_old_threshold = gc->live_after_mark/100 * MAJOR_GC_INC_RATIO;
     gc->full = FALSE;
   }
 
@@ -1449,7 +1449,7 @@ change_gen_gc_mode(mrb_state *mrb, mrb_gc *gc, mrb_bool enable)
   }
   else if (!is_generational(gc) && enable) {
     incremental_gc_until(mrb, gc, MRB_GC_STATE_ROOT);
-    gc->majorgc_old_threshold = gc->live_after_mark/100 * DEFAULT_MAJOR_GC_INC_RATIO;
+    gc->majorgc_old_threshold = gc->live_after_mark/100 * MAJOR_GC_INC_RATIO;
     gc->full = FALSE;
   }
   gc->generational = enable;