bake#ReadRecords errors on non-bake records

[mamachanko]

Describe the bug

bake#ReadRecords errors on non-bake records, e.g. the conventional .gitkeep or .gitignore or any other non-bake record

Reproduction steps

1. touch ./bake_records/.gitkeep
2. run [bake#ReadRecords](https://pkg.go.dev/github.com/pivotal-cf/kiln@v0.102.0/pkg/bake#ReadRecords) against ./bake_records
3. it errors

Expected behavior

1. touch ./bake_records/.gitkeep
2. run [bake#ReadRecords](https://pkg.go.dev/github.com/pivotal-cf/kiln@v0.102.0/pkg/bake#ReadRecords) against ./bake_records
3. it lists versions contained in ./bake_records

Additional context

No response