Minor docstring fixes
Minor docstring fixes

This removes some versionadded/versionchanged lines that were
unnecessary in a brand new function, but ended up there because of
copypasta. It also updates the output_encoding documentation to match
the updated docs from a recent PR that hasn't yet been merged from
2018.3 to develop.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt