Remove Noto Color Emoji fallback (#13838)

It's causing browser errors logged in Firefox under certain
circumstances, and I think we're better off recommending Linux users to
install a proper emoji font into their system.

Author: silverwind

docs/content/doc/help/faq.en-us.md

@@ -336,3 +336,7 @@ for the database_name and run `ALTER TABLE table_name CONVERT TO CHARACTER SET u
 for each table in the database.
 
 You will also need to change the app.ini database charset to `CHARSET=utf8mb4`.
+
+## Why are Emoji displaying only as placeholders or in monochrome
+
+Gitea requires the system or browser to have one of the supported Emoji fonts installed, which are Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol, Noto Color Emoji and Twemoji Mozilla. Generally, the operating system should already provide one of these fonts, but especially on Linux, it may be necessary to install them manually.

web_src/fonts/noto-color-emoji/LICENSE

@@ -132,14 +132,6 @@
   font-weight: 500;
 }
 
-@font-face {
-  font-family: "Noto Color Emoji";
-  src:
-    local("Noto Color Emoji"),
-    local("Noto-Color-Emoji"),
-    url("../fonts/noto-color-emoji/NotoColorEmoji.ttf") format("truetype");
-}
-
 textarea {
   font-family: var(--fonts-regular);
 }