Bump version to v0.5.6 for release

src/auto_archiver/version.py

@@ -3,7 +3,7 @@ _MAJOR = "0"
 _MINOR = "5"
 # On main and in a nightly release the patch should be one ahead of the last
 # released build.
-_PATCH = "5"
+_PATCH = "6"
 # This is mainly for nightly builds which have the suffix ".dev$DATE". See
 # https://semver.org/#is-v123-a-semantic-version for the semantics.
 _SUFFIX = ""