Don't cache the block return value

Let the matcher handle this if it needs to.

src/spectator/block.cr

@@ -1,6 +1,5 @@
 require "./expression"
 require "./label"
-require "./lazy"
 
 module Spectator
   # Represents a block from a test.
@@ -9,9 +8,6 @@ module Spectator
   # The label should be a string recognizable by the user,
   # or nil if one isn't available.
   class Block(T) < Expression(T)
-    # Cached value returned from the block.
-    @value = Lazy(T).new
-
     # Creates the block expression from a proc.
     # The *proc* will be called to evaluate the value of the expression.
     # The *label* is usually the Crystal code for the *proc*.
@@ -28,18 +24,10 @@ module Spectator
       super(label)
     end
 
-    # Retrieves the value of the block expression.
-    # This will be the return value of the block.
-    # The block is lazily evaluated and the value retrieved only once.
-    # Afterwards, the value is cached and returned by successive calls to this method.
-    def value
-      @value.get { call }
-    end
-
     # Evaluates the block and returns the value from it.
     # This method _does not_ cache the resulting value like `#value` does.
     # Successive calls to this method may return different values.
-    def call : T
+    def value : T
       @block.call
     end
   end