Remove `rescue` clause from `repository_size` helper

The repository size has since become calculated (and cached) more
intelligently, and this should no longer be necessary.

app/helpers/projects_helper.rb

@@ -202,11 +202,6 @@ module ProjectsHelper
   def repository_size(project = @project)
     size_in_bytes = project.repository_size * 1.megabyte
     number_to_human_size(size_in_bytes, delimiter: ',', precision: 2)
-  rescue
-    # In order to prevent 500 error
-    # when application cannot allocate memory
-    # to calculate repo size - just show 'Unknown'
-    'unknown'
   end
 
   def default_url_to_repo(project = @project)