clean up #ast_info.pre_render_asts

it is no longer used.

include/erlydtl_ext.hrl

@@ -46,8 +46,8 @@
           custom_tags = [],
           var_names = [],
           def_names = [],
-          const_names = [],
-          pre_render_asts = []}).
+          const_names = []
+         }).
 
 -record(treewalker, {
           counter = 0,

src/erlydtl_beam_compiler.erl

@@ -462,7 +462,6 @@ custom_forms(Dir, Module, Functions, AstInfo) ->
     [erl_syntax:revert(X)
      || X <- [ModuleAst, ExportAst, SourceFunctionAst, DependenciesFunctionAst,
               TranslatableStringsFunctionAst | FunctionAsts]
-            ++ AstInfo#ast_info.pre_render_asts
     ].
 
 stringify(BodyAst, #dtl_context{ binary_strings=BinaryStrings }) ->