fix(targets): Target parser should accept both x and X

[BYK]

Changes the targets parser to be case insensitive so we handle both x and X as checked-off.

Alternatively, we can make the char-class [ xX].

Alternatively we can make the entire regex case-insensitive.

This fixes the issue reported here: getsentry/craft#611 (comment) (second item)

Related failure: #5882

[BYK]

cc @stephanie-anderson -- Not sure why your edit got in as a X instead of the regulat x. Did you click on the checkbox from the UI or manually edited the issue description?

[BYK]

FYI validated that this is the case by looking at the logs and testing the regexp: https://regex101.com/r/ivTbZM/1

[asottile-sentry]

Alternatively, we can make the char-class [ xX].

let's do this just for specificity sake

[BYK]

@asottile-sentry done

[BYK]

We should probably retry the failing release right after merging this as a test (and just fix that half-release)

[asottile-sentry]

[romtsn]

We should probably retry the failing release right after merging this as a test (and just fix that half-release)

#5882 success!

[kahest]

thank you @BYK!