Martin von Zweigbergk <martinvonz@google.com> [Tue, 23 Feb 2021 22:58:30 -0800] rev 46645
narrow: remove assertion about working copy being clean
The user can always modify the working copy, including while they're
running `hg tracked --remove-include <path>`. Nothing really bad
happens when they do that, and we already have code for printing a
nice warning, so we can safely remove the assertion we had.
Differential Revision: https://phab.mercurial-scm.org/D10063