Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
	Gemfile

Solved conflicts by using upstream's line for posix-spawn

app/javascript/mastodon/locales/ja.json

@@ -287,7 +287,7 @@
   "upload_button.label": "メディアを追加",
   "upload_form.description": "視覚障害者のための説明",
   "upload_form.focus": "焦点",
-  "upload_form.undo": "やり直す",
+  "upload_form.undo": "削除",
   "upload_progress.label": "アップロード中...",
   "video.close": "動画を閉じる",
   "video.exit_fullscreen": "全画面を終了する",