(Maint) Cleaning up .sync.yml file

These few changes sprung up as a result of major changes in our
changelog generator usage. It no longer behaves as it previously did and,
therefore, there is no more need for this gem nor the tag option.

Author: LukasAud

.sync.yml

@@ -5,12 +5,10 @@ appveyor.yml:
   delete: true
 
 Gemfile:
-  optional:
-    ":development":
-    - gem: github_changelog_generator
-      version: '= 1.15.2'
 Rakefile:
   changelog_max_issues: 500
+  extra_disabled_lint_checks:
+    - anchor_resource
 spec/spec_helper.rb:
   mock_with: ":rspec"
   coverage_report: true
@@ -28,7 +26,3 @@ spec/spec_helper.rb:
   unmanaged: false
 .travis.yml:
   delete: true
-changelog_since_tag: '5.0.1'
-Rakefile:
-  extra_disabled_lint_checks:
-    - anchor_resource