take out unused rake brand_configs:fingerprints task

we stopped using this in 
c3386397ef

test plan:
webpack build should work as normal

Change-Id: I47eab08811c5aa28b7d0c5bd1a70253bd457d134
Reviewed-on: https://gerrit.instructure.com/84827
Tested-by: Jenkins
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Ryan Shaw <ryan@instructure.com>
QA-Review: Ryan Shaw <ryan@instructure.com>

lib/tasks/brand_configs.rake

@@ -31,13 +31,4 @@ namespace :brand_configs do
     # This'll pick up on all those written brand_configs and compile their css.
     BrandableCSS.compile_all!
   end
-
-  # We need this when webpack is building handlebars files to get the fingerprints
-  # for a given jst template.  this was easier for now than rewriting that extraction
-  # in node.
-  task :fingerprints, [:bundle] do |t, args|
-    bundle = args[:bundle]
-    puts BrandableCSS.all_fingerprints_for(bundle).to_json
-  end
-
 end