make the label useful on the folder browing tree
make the label useful on the folder browing tree

fixes ADMIN-2229

test plan:
- Using a SR on the files page, the label for the folder tree should say
  "Folder Browing Tree" instead of instructions for using the tree.

Change-Id: I94f001b03ea869cb90d97c0173c38e00b4a73103
Reviewed-on: https://gerrit.instructure.com/171960
Tested-by: Jenkins
Reviewed-by: Carl Kibler <7c2b40129dd885a147d5b2dda56dda016b9a8f57@instructure.com>
QA-Review: Daniel Sasaki <ae19fabf7fe19dff310008c9b6a4d2ec84d311d8@instructure.com>
Product-Review: Daniel Sasaki <ae19fabf7fe19dff310008c9b6a4d2ec84d311d8@instructure.com>

djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms