Fix command substitution syntax in archive examples

[JiaqiFan42]

Make the command subsititution syntax modern and consistent. (e.g. the example on line 282 already used the "$(...)" syntax. I suppose it's better to make it consistent.)

• I provide my work under the project license.
• I grant such license of my work as is required for the purposes of future print editions to Ben Straub and Scott Chacon.

Changes

• Make the command subsititution syntax modern and consistent. (e.g. the example on line 282 already used the "$(...)" syntax. I suppose it's better to make it consistent.)

Context