Remove now redundant configs

Since deprecations are enabled by default.

spec/install/gemfile/sources_spec.rb

@@ -25,7 +25,6 @@
           gem "rack-obama"
           gem "rack"
         G
-        bundle "config set major_deprecations true"
       end
 
       it "warns about ambiguous gems, but installs anyway, prioritizing sources last to first", :bundler => "< 2" do
@@ -55,7 +54,6 @@
           gem "rack-obama"
           gem "rack", "1.0.0" # force it to install the working version in repo1
         G
-        bundle "config set major_deprecations true"
       end
 
       it "warns about ambiguous gems, but installs anyway", :bundler => "< 2" do
@@ -249,7 +247,6 @@
           end
 
           it "installs from the other source and warns about ambiguous gems", :bundler => "< 2" do
-            bundle "config set major_deprecations true"
             bundle :install
             expect(out).to have_major_deprecation a_string_including("Your Gemfile contains multiple primary sources.")
             expect(out).to include("Warning: the gem 'rack' was found in multiple sources.")

spec/other/major_deprecation_spec.rb

@@ -5,8 +5,6 @@
   let(:warnings_without_version_messages) { warnings.gsub(/#{Spec::Matchers::MAJOR_DEPRECATION}Bundler will only support ruby(gems)? >= .*/, "") }
 
   before do
-    bundle "config set major_deprecations true"
-
     create_file "gems.rb", <<-G
       source "file:#{gem_repo1}"
       ruby #{RUBY_VERSION.dump}