Relax thresholds for array, object, and string compaction verification

These tests failed with RHEL10

https://rubyci.s3.amazonaws.com/rhel10/ruby-master/log/20250828T093003Z.fail.html.gz

Author: hsbt

test/ruby/test_gc_compact.rb

@@ -324,7 +324,7 @@ def test_moving_arrays_up_heaps
       }.resume
 
       stats = GC.verify_compaction_references(expand_heap: true, toward: :empty)
-      assert_operator(stats.dig(:moved_up, :T_ARRAY) || 0, :>=, ARY_COUNT - 10)
+      assert_operator(stats.dig(:moved_up, :T_ARRAY) || 0, :>=, ARY_COUNT - 15)
       refute_empty($arys.keep_if { |o| ObjectSpace.dump(o).include?('"embedded":true') })
     end;
   end
@@ -356,7 +356,7 @@ def add_ivars
 
       stats = GC.verify_compaction_references(expand_heap: true, toward: :empty)
 
-      assert_operator(stats.dig(:moved_up, :T_OBJECT) || 0, :>=, OBJ_COUNT - 10)
+      assert_operator(stats.dig(:moved_up, :T_OBJECT) || 0, :>=, OBJ_COUNT - 15)
       refute_empty($ary.keep_if { |o| ObjectSpace.dump(o).include?('"embedded":true') })
     end;
   end
@@ -377,7 +377,7 @@ def test_moving_strings_up_heaps
 
       stats = GC.verify_compaction_references(expand_heap: true, toward: :empty)
 
-      assert_operator(stats[:moved_up][:T_STRING], :>=, STR_COUNT - 10)
+      assert_operator(stats[:moved_up][:T_STRING], :>=, STR_COUNT - 15)
       refute_empty($ary.keep_if { |o| ObjectSpace.dump(o).include?('"embedded":true') })
     end;
   end