feat: source sidekiq-batch from GitHub repository (#654)

Support for Sidekiq v7 has been landed in the repository
(breamware/sidekiq-batch#89 &
breamware/sidekiq-batch#85), but not yet
released - hopefully that'll happen soon, but in the meantime I'm
switching us to pull from the repository because
1. it sounds like that includes some further fixes which might be useful
to us
2. the ubuntu-24 stack on Heroku no longer has `git` at runtime which
looks to be causing our deployment to fail because
`sidekiq-batch.gemspec` tries to do `git ls-remote -z` for determining
the files to include; we might still run into issues because we're
technically still using `git`, but I'm hoping this moves our usage into
the "build" phase where `git` should still be available...

Gemfile

@@ -24,7 +24,7 @@ gem "raygun4ruby"
 gem "redis"
 gem "sassc-rails"
 gem "sidekiq"
-gem "sidekiq-batch", path: "vendor/gems/sidekiq-batch"
+gem "sidekiq-batch", github: "breamware/sidekiq-batch" # required for sidekiq v7, as changes have not yet been released
 gem "sqlite3"
 gem "turbolinks"
 gem "webpacker", "~> 5.0"

Gemfile.lock

@@ -1,8 +1,9 @@
-PATH
-  remote: vendor/gems/sidekiq-batch
+GIT
+  remote: https://github.com/breamware/sidekiq-batch.git
+  revision: f2ef0289ea23e652797741de96506957535099ff
   specs:
     sidekiq-batch (0.1.9)
-      sidekiq (>= 3, < 8)
+      sidekiq (>= 7, < 8)
 
 GEM
   remote: https://rubygems.org/