documentation refers to OS and OSRelease, bug reports use DistroRelease

The documentation (doc/data-format.tex) describes the OS and OSRelease fields:

    \item [OS:] (optional) Name of the operating system. On LSB compliant
    systems, this can be determined with \verb!lsb_release -si!.

    \item [OSRelease:] (optional) Release version of the operating system. On
    LSB compliant systems, this can be determined with \verb!lsb_release -sr!.

But these are not included in bug reports. Instead, the DistroRelease field is included, and its value is constructed from the output of lsb_release -sir in report.py:

    def add_os_info(self):
        '''Add operating system information.

        This adds:
        - DistroRelease: lsb_release -sir output
        - Architecture: system architecture in distro specific notation
        - Uname: uname -srm output
        - NonfreeKernelModules: loaded kernel modules which are not free (if
            there are none, this field will not be present)
        '''
        p = subprocess.Popen(['lsb_release', '-sir'], stdout=subprocess.PIPE,
            stderr=subprocess.PIPE, close_fds=True)
        self['DistroRelease'] = p.communicate()[0].decode().strip().replace('\n', ' ')

        u = os.uname()
        self['Uname'] = '%s %s %s' % (u[0], u[2], u[4])
        self['Architecture'] = packaging.get_system_architecture()

The documentation should be updated to reflect the use of DistroRelease instead of OS and OSRelease.