* Improve label edit buttons labels
Previously when editing the buttons in the "Edit Label" modal were a
strange "Update" and "No". Improved them to "Save" and "Cancel".
Also fixed indentation in the template file, recommended to view changes
with the "Hide whitespace changes" option enabled on GitHub.
* remove unnecessary button icon
Co-authored-by: techknowlogick <techknowlogick@gitea.io>