Updated Backups (markdown)

Backups.md

@@ -28,7 +28,7 @@ In OpenKeychain, backups are encrypted using:
 ## Design decisions
 * Dashes are included to ease decryption using OpenPGP implementations that don't offer special dialogs for entering backup codes and only support single text fields for entering passwords.
 * Security level: Possible combinations are 34^24 = 2^122.10. This is enough to be protected against offline brute force attacks. You can get a rough estimate using https://www.grc.com/haystack.htm .
-* Using only upper case letters, no lower case letters and no numbers
+* Using only upper case letters, no lower case letters
   * Using mixed upper and lower case makes it much more difficult to recall the characters from short term memory. Consider someone reading them aloud, it is required to say for every letter if it's upper or lower case. Memorizing things in short term memory works similar to reading something aloud, which makes the mixed upper/lower case backup codes double as difficult to remember than upper-case-only backup codes.
   * They look like serial numbers, like they were used for Windows, when using upper case only. Many people know serial numbers and are thus comfortable with using these.
 * Dividing into 4-character chunks