fix(docker): govips requires imagemagick to load BMP files now

For details see: https://github.com/davidbyttow/govips/commit/dd8aed88c0d8a8963b1513f410657b5777df0fed
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f