README: bump pinned-version example to 0.8.5

Keep the "specific version" GHCR example current with the latest release.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: cdibona

README.md

@@ -269,7 +269,7 @@ Every GitHub Release builds and pushes a container image via
 
 ```
 ghcr.io/cdibona/ferrynotifier:latest    # newest release
-ghcr.io/cdibona/ferrynotifier:0.8.4     # a specific version
+ghcr.io/cdibona/ferrynotifier:0.8.5     # a specific version
 ```
 
 If the package is private, log in first with a token that has `read:packages`: