bootstrap: elide original require_bootstrap_uptodate setting.

The pre-merge expanded bootstrap.in from upstream has several
occurrences of many section headers, so we have to use the -e
option of our merge-sections script to elide the original
bootstrap.in definition of require_bootstrap_uptodate, so that
our improved version takes precedence.
* bootstrap.conf (require_bootstrap_uptodate): When generating
the merged bootstrap script elide require_bootstrap_uptodate
setting.
* bootstrap: Regenerate.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>