lsstdocushare extension shouldn't use ls.st for lsst.io-based documents

[jonathansick]

For lsst.io-based technotes, the sqr, dmtn, etc roles should point directly to the lsst.io URLs rather than going through ls.st. This improves performance for users, and is also more reliable (as of this writing, ls.st links for technotes are down because a migration of ls.st resulting in some rewrite rules being dropped; https://jira.lsstcorp.org/browse/IHS-3472)