lint fails on main

[jku]

sigstore/dsse.py:191: error: Unused "type: ignore" comment  [unused-ignore]
sigstore/dsse.py:220: error: Argument "keyid" to "Signature" has incompatible type "None"; expected "str"  [arg-type]
sigstore/dsse.py:249: error: Unused "type: ignore" comment  [unused-ignore]
sigstore/_internal/trustroot.py:111: error: Argument 1 to "load_der_public_key" has incompatible type "bytes | None"; expected "bytes"  [arg-type]
sigstore/_internal/trustroot.py:115: error: Argument 1 to "load_der_public_key" has incompatible type "bytes | None"; expected "bytes"  [arg-type]
sigstore/models.py:246: error: Argument "inclusion_promise" to "TransparencyLogEntry" has incompatible type "InclusionPromise | None"; expected "InclusionPromise"  [arg-type]
sigstore/models.py:498: error: Unused "type: ignore" comment  [unused-ignore]

This related to sigstore-protobuf 0.3.2 release. nothing much seems to have changed in the release but py.typed was added

[jku]

Other issues seem like trivial fixes but this is a bit strange:
dsse.py:220: error: Argument "keyid" to "Signature" has incompatible type "None"; expected "str" [arg-type]

keyid is documented as optional but is not actually annotated as such: https://github.com/sigstore/protobuf-specs/blob/2c9be05fb6720b5e07b5c96e99524abed9e0d14b/protos/envelope.proto#L51

Filing an issue in protobuf seems appropriate but I think we'll just have to live ẃith a non-optional keyid in this code base as well?

[jku]

sigstore/protobuf-specs#324