message: Update LangRef to reflect int/flaot attribute specification changes.
diff: @@ -842,8 +842,8 @@ Attributes have a name, and their values are represented by the following forms:
  ``` {.ebnf}
  attribute-value ::= bool-literal
  - | integer-literal
  - | float-literal
  + | integer-literal ( `:` (index-type | integer-type) )?
  + | float-literal ( `:` float-type )?
  | string-literal
  | affine-map
  | type
  