refactor: move scaladoc .gitignore to the root one

None of the other modules have their own gitignore so to avoid any
confusion this just moves the single entry in the scaladoc one to the
main one and then removes the scaladoc one.

Author: ckipp01

.gitignore

@@ -95,3 +95,7 @@ contributors.js
 content-contributors.css
 docs/_spec/_site/
 docs/_spec/.jekyll-metadata
+
+# scaladoc related
+scaladoc/output/
+