Remove normalize_input call in the usage snippet in the README

The call is unnecessary because normalization is done in the `parse_stylesheet` procedure, as per the [Syntax] specification.

Author: amn

README.md

@@ -29,8 +29,8 @@ It should go without saying that whether you choose to install the package with
 The code snippet below demonstrates obtaining of a _parse tree_ (in the `stylesheet` variable) by parsing the file `example.css`:
 
 ```python
-from csspring.parsing import normalize_input, parse_stylesheet
-stylesheet = parse_stylesheet(normalize_input(open('example.css', newline=''))))) # The `newline=''` argument prevents default re-writing of newline sequences in input — per the CSS Syntax spec., parsing does filtering of newline sequences so no rewriting by `open` is necessary or desirable
+from csspring.parsing import parse_stylesheet
+stylesheet = parse_stylesheet(open('example.css', newline='')))) # The `newline=''` argument prevents default re-writing of newline sequences in input — per the CSS Syntax spec., parsing does filtering of newline sequences so no rewriting by `open` is necessary or desirable
 ```
 
 ## Documentation