Fix the two "marker"-alike cases (for package `python_version`)
for test_nowarn_accidental_env_marker_misconfig to use `<3` rather
than `<'3'`.  The latter maps to the version `'3'` which is not a valid
version and therefore causes an error with packaging-22.0+.

See the discussion at
https://github.com/pypa/setuptools/commit/506e7e7e1cac6a5d534184d35a20a73e9dd58045#r97577660

Fix the install_requires used in test_dist_info to use the dangling
syntax, in order to correctly handle markers.  This fixes syntax error
when parsed by packaging-22.0+, as well as setuptools warning:

```
UserWarning: One of the parsed requirements in `install_requires` looks like a valid environment marker: \'sys_platform != "linux"\'
Make sure that the config is correct and check https://setuptools.pypa.io/en/latest/userguide/declarative_config.html#opt-2
  warnings.warn(msg, UserWarning)\n'
```

… to be automatically added to the sdist