Mark `brew bump` test with `:needs_network.

Library/Homebrew/test/dev-cmd/bump_spec.rb

@@ -8,7 +8,7 @@ describe "brew bump" do
     it_behaves_like "parseable arguments"
   end
 
-  describe "formula", :integration_test do
+  describe "formula", :integration_test, :needs_network do
     it "returns data for single valid specified formula" do
       install_test_formula "testball"