This updates our zlint dependency to 8093f211c4 - the tip of master at the time of writing. Notably this brings in a gTLD map that has effective periods so cert-checker can catch issuance for removed gTLDs after their removal date.
Unit tests are confirmed to pass:
```
$> git rev-parse HEAD
8093f211c43679b1ade744d238a02ba1f0c07371
$> go test ./...
ok github.com/zmap/zlint 0.284s
? github.com/zmap/zlint/cmd/zlint [no test files]
? github.com/zmap/zlint/cmd/zlint-gtld-update [no test files]
ok github.com/zmap/zlint/lints 0.165s
ok github.com/zmap/zlint/util 0.005s
```
Notably this brings an [updated gTLD list](https://github.com/zmap/zlint/pull/233).
Tests are confirmed to pass:
```
go test ./...
ok github.com/zmap/zlint 0.157s
? github.com/zmap/zlint/cmd/zlint [no test files]
ok github.com/zmap/zlint/lints 0.130s
ok github.com/zmap/zlint/util 0.005s
```
Switch linting library to zmap/zlint.
```
github.com/zmap/zlint$ go test ./...
ok github.com/zmap/zlint 0.190s
? github.com/zmap/zlint/cmd/zlint [no test files]
ok github.com/zmap/zlint/lints 0.216s
ok github.com/zmap/zlint/util (cached)
```
Daniel McCarney