Add missing semicolon

[r6e]

Fixes #323

The build fails on the ruby:2.7.5-buster Docker image (and, presumably, other Linux distros using the same build chain) due to a missing semicolon. For some reason, the build does not fail on macOS.

Adding this semicolon allows the build to pass on the ruby:2.7.5-buster image, and it still passes on macOS as well.

[r6e]

The build failure looks like a config issue that wouldn't have anything to do with this change. Not really sure what, if anything, I should do about that.

[cs278]

Came here to suggest the same fix.

[casperisfine]

Thank you

[flavorjones]

I'm going to first ship a PR that adds a CI job that covers this branch. Please hold.

[flavorjones]

Success, failing CI: https://github.com/sparklemotion/sqlite3-ruby/runs/6880316208?check_suite_focus=true

I've now added that CI job into this PR. I expect the test for this feature will now fail ...

[flavorjones]

And added a commit to conditionally skip that test for sqlite < 3.29.0.

[flavorjones]

I'll also note that I have a large branch at #320 that cleans up CI and the C extension a bit, which also fixes the appveyor/windows builds, so I'm not worried about those failures right now.

[flavorjones]

Thank you! I'll poke the folks with gem push privileges to get a release out.