chore: Minor documentation fixes

Author: twpayne

assets/chezmoi.io/docs/user-guide/encryption/age.md

@@ -2,7 +2,7 @@
 
 chezmoi supports encrypting files with [age][age].
 
-Generate a key using the `age-keygen`:
+Generate a key using `chezmoi age-keygen`:
 
 ```console
 $ chezmoi age-keygen --output=$HOME/key.txt

assets/chezmoi.io/docs/user-guide/frequently-asked-questions/encryption.md

@@ -15,7 +15,7 @@ This can be achieved with the following process:
 First, change to chezmoi's root directory:
 
 ```sh
-chezmoi cd ~
+chezmoi cd
 ```
 
 Generate an age private key encrypted with a passphrase in the file