Revert "update README about farseerfc key"

archlinuxcn-keyring is now packaged by Felix Yan.

This reverts commit b084f50.

Author: oldherl

README.md

@@ -24,12 +24,6 @@ Import PGP Keys:
 sudo pacman -Sy && sudo pacman -S archlinuxcn-keyring
 ```
 
-Due to a developer's retirement, newly installed systems need to manually trust farseerfc's key:
-
-```bash
-sudo pacman-key --lsign-key "[email protected]"
-```
-
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