Revert "Don't show a deprecation warning for EnsureNode#branch just yet"

This reverts commit 3a7c069.

Author: dvandersluis

lib/rubocop/ast/node/ensure_node.rb

@@ -6,11 +6,24 @@ module AST
     # node when the builder constructs the AST, making its methods available
     # to all `ensure` nodes within RuboCop.
     class EnsureNode < Node
+      DEPRECATION_WARNING_LOCATION_CACHE = [] # rubocop:disable Style/MutableConstant
+      private_constant :DEPRECATION_WARNING_LOCATION_CACHE
+
       # Returns the body of the `ensure` clause.
       #
       # @return [Node, nil] The body of the `ensure`.
       # @deprecated Use `EnsureNode#branch`
       def body
+        first_caller = caller(1..1).first
+
+        unless DEPRECATION_WARNING_LOCATION_CACHE.include?(first_caller)
+          warn '`EnsureNode#body` is deprecated and will be changed in the next major version of ' \
+               'rubocop-ast. Use `EnsureNode#branch` instead to get the body of the `ensure` branch.'
+          warn "Called from:\n#{caller.join("\n")}\n\n"
+
+          DEPRECATION_WARNING_LOCATION_CACHE << first_caller
+        end
+
         branch
       end