Merge upstream changes

[polyamAdmin]

This reverts #573 as the issue seems to be solved.

Conflicts:

• Gemfile.lock Upstream bumped charlock_holmes. Polyam-glitch uses a temporary fork to fix an issue with ICU on arch systems. Reverted back to charlock_holmes.
• app/javascript/flavours/glitch/styles/components.scss Upstream refactored styling for collapsed toots. Polyam-glitch had some extra styles for backgrounds and reactions. Ported upstream change.
• app/javascript/mastodon/locales/en-GB.json A modified string got deleted. Deleted like upstream.
• app/javascript/mastodon/locales/en.json Upstream changed casing in a modified string. Changed casing like upstream.

Ported changes:

• 547e97945df0abc68dc473ed60d2faeb2feb2b06
• 2c7eed1fa1e7af72dd03a041a60f2cfd42e913e0
• 8c0ff6498e090a2919e8f8104339796ed2d3d212
• 8160a655a528856f87b8d0174bce54c78a7af4be
• d612daee97d95c67009f7e6e3be25f1a2a5aa352
• 096057b845f27fd6090915b22c8688a6eeb22e28
• 98185247b85cb2fa6b0dc9c5f5be7d22f3db7a24
• ea6c455e81f9f01a64adf123d0a4f820c6e67f97
• 935b955b156f6313e1a4555dbb7b0661c2de1e0a
• 6d6064d2c0242c6b923b79db05fefa3d8c581827

Additional changes:

• d8c4ebeef490ff54841440e6b770fafa9a00aba2 (Fix merge)
• d61ae40ad01e88e773d415f15224f5764d1cae93 (I don't remember why I did this)