Bump webpush from 0.3.5 to 0.3.6 (#9783)

Bumps [webpush](https://github.com/zaru/webpush) from 0.3.5 to 0.3.6.
- [Release notes](https://github.com/zaru/webpush/releases)
- [Changelog](https://github.com/zaru/webpush/blob/master/CHANGELOG.md)
- [Commits](zaru/webpush@v0.3.5...v0.3.6)

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

Gemfile.lock

@@ -637,7 +637,7 @@ GEM
       activesupport (>= 4.2)
       rack-proxy (>= 0.6.1)
       railties (>= 4.2)
-    webpush (0.3.5)
+    webpush (0.3.6)
       hkdf (~> 0.2)
       jwt (~> 2.0)
     websocket-driver (0.7.0)