make the string filter logic a little clearer

`input_name_simple` is only ever called when the method already matches
a search condition so there's no need for it

Author: seanlinsley

lib/active_admin/inputs/filter_check_boxes_input.rb

@@ -13,7 +13,7 @@ def selected_values
 
       # Add whitespace before label
       def choice_label(choice)
-        " #{super(choice)}"
+        ' ' + super
       end
 
       # Don't wrap in UL tag

lib/active_admin/inputs/filter_string_input.rb

@@ -4,21 +4,19 @@ class FilterStringInput < ::Formtastic::Inputs::StringInput
       include FilterBase
       include FilterBase::SearchMethodSelect
 
+      # If the filter method includes a search condition, build a normal string search field.
+      # Else, build a search field with a companion dropdown to choose a search condition from.
       def to_html
         if search_conditions =~ method.to_s
           input_wrapping do
             label_html <<
-            builder.text_field(input_name_simple, input_html_options)
+            builder.text_field(method, input_html_options)
           end
         else
-          super
+          super # SearchMethodSelect#to_html
         end
       end
 
-      def input_name_simple
-        method.to_s.match(search_conditions) ? method : "#{method}_contains"
-      end
-
       def search_conditions
         /_(contains|starts_with|ends_with)\z/
       end