Tiny fixes to ignore sqlite3 test files and warnings (#537)

* Ignore "test.sqlite3-shm", "test.sqlite3-wal" files

Generated by rails/rails#49349

* Fix warning: `*' interpreted as argument prefix

```
app/models/concerns/turbo/broadcastable.rb:297: warning: `*' interpreted as argument prefix
```

* Fix warning: assigned but unused variable - board

```
test/streams/broadcastable_test.rb:304: warning: assigned but unused variable - board
```

.gitignore

@@ -1,3 +1,7 @@
 *.gem
 /node_modules
 Gemfile.lock
+
+# Generated by rails/rails#49349
+*.sqlite3-shm
+*.sqlite3-wal

app/models/concerns/turbo/broadcastable.rb

@@ -294,7 +294,7 @@ def broadcast_prepend(target: broadcast_target_default, **rendering)
   end
 
   def broadcast_refresh_to(*streamables)
-    Turbo::StreamsChannel.broadcast_refresh_to *streamables unless suppressed_turbo_broadcasts?
+    Turbo::StreamsChannel.broadcast_refresh_to(*streamables) unless suppressed_turbo_broadcasts?
   end
 
   def broadcast_refresh

test/streams/broadcastable_test.rb

@@ -301,7 +301,7 @@ class Turbo::BroadcastableBoardTest < ActionCable::Channel::TestCase
   test "creating a board broadcasts refreshes to a channel using models plural name when creating" do
     assert_broadcast_on "boards", turbo_stream_action_tag("refresh") do
       perform_enqueued_jobs do
-        board = Board.create!(name: "Board")
+        Board.create!(name: "Board")
         Turbo::StreamsChannel.refresh_debouncer_for(["boards"]).wait
       end
     end