Bump webpush from 0.3.6 to 0.3.7 (mastodon#10205)

Bumps [webpush](https://github.com/zaru/webpush) from 0.3.6 to 0.3.7.
- [Release notes](https://github.com/zaru/webpush/releases)
- [Changelog](https://github.com/zaru/webpush/blob/master/CHANGELOG.md)
- [Commits](zaru/webpush@v0.3.6...v0.3.7)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Gemfile.lock

@@ -641,7 +641,7 @@ GEM
  activesupport (>= 4.2)
  rack-proxy (>= 0.6.1)
  railties (>= 4.2)
- webpush (0.3.6)
+ webpush (0.3.7)
  hkdf (~> 0.2)
  jwt (~> 2.0)
  websocket-driver (0.7.0)