Use non deprecated ways ourselves

The previous change of removing the deprecations feature flag caused
these specs to start failing, because they simulate older rubies that
didn't print deprecations under the old feature flag setup.

spec/bundler/cli_spec.rb

@@ -97,7 +97,7 @@
     let(:bundler_version) { "1.1" }
     let(:latest_version) { nil }
     before do
-      bundle! "config --global disable_version_check false"
+      bundle! "config set --global disable_version_check false"
 
       simulate_bundler_version(bundler_version)
       if latest_version
@@ -132,13 +132,13 @@
       end
 
       context "and disable_version_check is set" do
-        before { bundle! "config disable_version_check true" }
+        before { bundle! "config set disable_version_check true" }
         include_examples "no warning"
       end
 
       context "running a parseable command" do
         it "prints no warning" do
-          bundle! "config --parseable foo"
+          bundle! "config get --parseable foo"
           expect(last_command.stdboth).to eq ""
 
           bundle "platform --ruby"