Treat pcsc::Error::NoSmartcard as a "YubiKey disconnected" error

Some SmartCard readers report this error when no SmartCard is inserted,
so we need to check for it when filtering for connected YubiKeys (along
with `pcsc::Error::RemovedCard` which some _other_ SmartCard readers
report instead).

Closes str4d/age-plugin-yubikey#81.

CHANGELOG.md

@@ -11,6 +11,8 @@ to 0.3.0 are beta releases.
 - When `age-plugin-yubikey` assists the user in changing their PIN from the
   default PIN, it no longer tells the user that PINs shorter than 6 characters
   are allowed, and instead loops until the user enters a PIN of valid length.
+- More kinds of SmartCard readers are ignored when they have no SmartCard
+  inserted.
 
 ## [0.3.2] - 2023-01-01
 ### Changed