Improve SETA maintenance documentation (#2757)
Improve SETA maintenance documentation (#2757)

The maintenance section was not addressing that data can take a while before the different scheduled processes bring the data into the right tables.

This addresses documenting how to:

* Update the runnable jobs table
* Update the job priority table
tojon/treeherder,KWierso/treeherder,tojon/treeherder,KWierso/treeherder,tojon/treeherder,tojon/treeherder,tojonmz/treeherder,edmorley/treeherder,KWierso/treeherder,edmorley/treeherder,tojonmz/treeherder,KWierso/treeherder,tojonmz/treeherder,edmorley/treeherder,tojonmz/treeherder,edmorley/treeherder,tojonmz/treeherder,tojonmz/treeherder