Remove wrong line hint for 'fields-bugs-field-does-not-refer-to-debian-infrastructure'

The tag fields-bugs-field-does-not-refer-to-debian-infrastructure includes a line number as a hint, but that number is incorrect. In the test fields-bugs-field-does-not-refer-to-debian-infrastructure, the offending field was located in line 9 of the generated control file and not in line 11, as the tag said. The line number appeared unrelated. It was removed.

At the time of writing, the tag did not appear in the wild. The error could not be corroborated outside the Lintian test suite.