Don't check for maxlength when collapsing the selection.
Apparently in some situations it might not be set? Not super familiar
with this code.
Differential Revision: https://phabricator.services.mozilla.com/D230516
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1933919
gecko-commit: fa34a24cd93f2f33cdf6a1bba8f9ec420653cbbc
gecko-reviewers: masayuki