Avoid using subject with structs

spec/spectator/lazy_spec.cr

@@ -1,15 +1,15 @@
 require "../spec_helper"
 
 Spectator.describe Spectator::Lazy do
-  subject { Spectator::Lazy(Int32).new }
-
   it "returns the value of the block" do
-    expect { subject.get { 42 } }.to eq(42)
+    lazy = Spectator::Lazy(Int32).new
+    expect { lazy.get { 42 } }.to eq(42)
   end
 
   it "caches the value" do
+    lazy = Spectator::Lazy(Int32).new
     count = 0
-    expect { subject.get { count += 1 } }.to change { count }.from(0).to(1)
+    expect { lazy.get { count += 1 } }.to change { count }.from(0).to(1)
-    expect { subject.get { count += 1 } }.to_not change { count }
+    expect { lazy.get { count += 1 } }.to_not change { count }
   end
 end