Remove the `browse_everything/browse_everything` SCSS deprecation message

[jrgriffiniii]

@import browse_everything/browse_everything is deprecated, please @import browse_everything_bootstrap3 is issued from apps which mount the engine from this Gem. Please see https://github.com/samvera/browse-everything/blob/master/app/assets/stylesheets/browse_everything/_browse_everything.scss#L1