fix(NcEmojiPicker): adjust hover effects to new design

[Antreesy]

☑️ Resolves

• Fix hover effects on emoji buttons
• Added fallback for Nextcloud <= v29

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 3️⃣ Backport to next requested with a Vue 3 upgrade

[susnux]

I am not sure but was there not a design review call where it was said that round outline makes sense for emoji?

(Changes look good, just want to make sure this is what designer intended)

[ShGKme]

I'd keep it rounded

[marcoambrosini]

@susnux @ShGKme I think they look fine less rounded, like the reaction buttons in talk right now

[susnux]

I really do not care, both are fine. Noticed that e.g. messengers like Telegram also have "angular" hover effect.
Changes are clean 👍

(To cite a user I asked: "IPhone users would prefer the round one, Android users the angular one.")

[Antreesy]

/backport to next