Remove DummyMatchData

No longer needed since MatchData was changed to non-abstract.

src/spectator/matchers/dummy_match_data.cr

@@ -1,32 +0,0 @@
-module Spectator::Matchers
-  # Match data 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 struct DummyMatchData < MatchData
-    # Creates the match data.
-    def initialize
-      super(false)
-    end
-
-    # Dummy values.
-    def named_tuple
-      {
-        you: "shouldn't be calling this.",
-      }
-    end
-
-    # Dummy message.
-    def message
-      "You shouldn't be calling this."
-    end
-
-    # Dummy message
-    def negated_message
-      "You shouldn't be calling this."
-    end
-  end
-end