settings: remove check on extensions.bootstrappedAddons

The check works on the en_US bundle, but not on the localized bundles
which have something like this in this setting:
{"langpack-nl@firefox.mozilla.org":{"version":"24.8.0","type":"locale",
"descriptor":"/home/testtestsuite/tbb-testsuite/tmp/ie0y0RPLZp/
tor-browser_nl/Data/Browser/profile.default/extensions/langpack-nl@firefox
.mozilla.org.xpi"}}
setting.js: uncomment security.nocertdb

Patch on ticket #12998 has been merged, so we can uncomment this.