docs: no code highlighting for HTTP responses
    
    The Pygments lexer for 'http' only supports HTTP *requests*, not
    responses. It's expecting the block to start with an HTTP method like
    GET, etc. If we try to highlight HTTP responses, it causes a Sphinx
    warning like this:
    
        docs/api.rst:1: WARNING: Could not lex literal_block as "http". Highlighting skipped.