[3.14] gh-119452: Remove select, skip 'truncated' test

[encukou]

This removes the select added in commit 29c657a.

As Greg put it in https://github.com/python/cpython/pull/119455/files#r2580052775:

why select at all here given we just want to block on reading another chunk?
if the socket closes or errors, that'd return anyways.

This makes the function wait forever for the query body. Thus, the new test 'test_large_content_length_truncated' times out. This was the case before the fix, too.

• Issue: OOM a potential denial of service in the CGI server on Windows #119452

[encukou]

#142180 instead uses timeout for each iteration, if the user sets it