Remove dummy example

src/spectator/dummy_example.cr

@@ -1,37 +0,0 @@
-require "./runnable_example"
-
-module Spectator
-  # Example that does nothing.
-  # This is to workaround a Crystal compiler bug.
-  # See: [Issue 4225](https://github.com/crystal-lang/crystal/issues/4225)
-  # If there are no concrete implementations of an abstract class,
-  # the compiler gives an error.
-  # The error indicates an abstract method is undefined.
-  # This class shouldn't be used, it's just to trick the compiler.
-  private class DummyExample < RunnableExample
-    # Dummy description.
-    def what : Symbol | String
-      "DUMMY"
-    end
-
-    # Dummy symbolic flag.
-    def symbolic? : Bool
-      false
-    end
-
-    # Dummy source.
-    def source : Source
-      Source.new(__FILE__, __LINE__)
-    end
-
-    # Dummy instance.
-    def instance
-      nil
-    end
-
-    # Dummy run that does nothing.
-    def run_instance
-      raise "You shouldn't be running this."
-    end
-  end
-end

src/spectator/includes.cr

@@ -23,7 +23,6 @@ require "./example_component"
 require "./example"
 require "./runnable_example"
 require "./pending_example"
-require "./dummy_example"
 
 require "./example_conditions"
 require "./example_hooks"