Remove support for fallback proc on last scope

This was introduced but never actually used. The introduction of environments.last as the fallback for unfound variables means this functionality is already broken

lib/liquid/context.rb

@@ -163,27 +163,11 @@ module Liquid
     def find_variable(key, raise_on_not_found: true)
       # This was changed from find() to find_index() because this is a very hot
       # path and find_index() is optimized in MRI to reduce object allocation
-      index = @scopes.find_index { |s| s.key?(key) }
-      scope = @scopes[index] if index
+      scope = (index = @scopes.find_index { |s| s.key?(key) }) && @scopes[index]
+      scope ||= (index = @environments.find_index { |s| s.key?(key) }) && @environments[index]
+      scope ||= {}
 
-      variable = nil
-
-      if scope.nil?
-        @environments.each do |e|
-          variable = lookup_and_evaluate(e, key, raise_on_not_found: raise_on_not_found)
-          # When lookup returned a value OR there is no value but the lookup also did not raise
-          # then it is the value we are looking for.
-          if !variable.nil? || @strict_variables && raise_on_not_found
-            scope = e
-            break
-          end
-        end
-      end
-
-      scope ||= @environments.last || @scopes.last
-      variable ||= lookup_and_evaluate(scope, key, raise_on_not_found: raise_on_not_found)
-
-      variable = variable.to_liquid
+      variable = lookup_and_evaluate(scope, key, raise_on_not_found: raise_on_not_found).to_liquid
       variable.context = self if variable.respond_to?(:context=)
 
       variable

test/integration/variable_test.rb

@@ -80,10 +80,7 @@ class VariableTest < Minitest::Test
     assigns['test'] = 'Tobi'
     assert_equal 'Hello Tobi', template.render!(assigns)
     assigns.delete('test')
-    e = assert_raises(RuntimeError) do
-      template.render!(assigns)
-    end
-    assert_equal "Unknown variable 'test'", e.message
+    assert_equal "Hello ", template.render!(assigns)
   end
 
   def test_multiline_variable