Add files in .flayignore and remove flog job

Signed-off-by: Rémy Coutable <remy@rymai.me>

.flayignore

 *.erb
 lib/gitlab/sanitizers/svg/whitelist.rb
+lib/gitlab/diff/position_tracer.rb
+app/services/akismet_service.rb

.gitlab-ci.yml

@@ -209,9 +209,6 @@ rubocop: *exec
 rake haml_lint: *exec
 rake scss_lint: *exec
 rake brakeman: *exec
-rake flog:
-  <<: *exec
-  allow_failure: yes
 rake flay:
   <<: *exec
   allow_failure: yes