UPGRADING: Fix database upgrade instructions

Oversight in commit 985795a2

.

Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>

UPGRADING

@@ -4,7 +4,7 @@ Upgrading
 From 1.9.1 to 2.0.0
 -------------------
 
-1. Add new "Users" table login date column:
+1. Add new "Users" table login date and PGP key columns:
 
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 ALTER TABLE Users ADD COLUMN LastLogin BIGINT NOT NULL DEFAULT 0;