drop rmagick, fixes #4594

This breaks the screenshot tool.

RMagick no longer compiles on recent ImageMagicks that have HDRI
support enabled.
Merge pull request #4900 from MrZYX/drop_rmagick

Drop rmagick
Fixed 4903 and not render vote form when user is not logged
Fix missing translation in #4905.
Merge pull request #4907 from goobertron/poll_i18n_fix

Fix missing translation in #4905
Merge pull request #4906 from hpetru/4903-poll-crash-spv

Fixed 4903 and not render vote form when user is not logged