Use correct license identifer in package.json

[cleptric]

I was trying to get rid of

warning package.json: License should be a valid SPDX license expression

when running the docs locally. While I didn't achieve this, the change still makes sense.

BSL-1.1 does not exists, the closest match is the Boost Software License 1.0.
In our case, this repo is licensed under the Business Source License 1.1, which short identifier is BUSL-1.1.

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Name	Status	Preview	Comments	Updated (UTC)
sentry-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 13, 2023 2:36pm

[chadwhitacre]

Good catch! :)