Make Rubocop happier about ActiveStorage

Running `rubocop activestorage` before this commit resulted in 20 offenses.
This commit only fixes:

- Trailing whitespace detected
- Space inside } missing
- Put one space between the method name and the first argument.

The other offenses are left since they are intentional according to
@georgeclaghorn (https://github.com/rails/rails/pull/30061#issuecomment-319999190)

activestorage/config/routes.rb

@@ -9,7 +9,7 @@ Rails.application.routes.draw do
   resolve("ActiveStorage::Attachment") { |attachment| route_for(:rails_blob, attachment.blob) }
 
 
-  get  "/rails/active_storage/variants/:signed_blob_id/:variation_key/*filename" => "active_storage/variants#show", as: :rails_blob_variation
+  get "/rails/active_storage/variants/:signed_blob_id/:variation_key/*filename" => "active_storage/variants#show", as: :rails_blob_variation
 
   direct :rails_variant do |variant|
     signed_blob_id = variant.blob.signed_id

activestorage/test/service/s3_service_test.rb

@@ -35,7 +35,7 @@ if SERVICE_CONFIGURATIONS[:s3] && SERVICE_CONFIGURATIONS[:s3][:access_key_id].pr
     end
 
     test "uploading with server-side encryption" do
-      config  = SERVICE_CONFIGURATIONS.deep_merge(s3: { upload: { server_side_encryption: "AES256" }})
+      config  = SERVICE_CONFIGURATIONS.deep_merge(s3: { upload: { server_side_encryption: "AES256" } })
       service = ActiveStorage::Service.configure(:s3, config)
 
       begin