Remove GITLAB_TEMPFILE_IMMEDIATE_UNLINK env var

We have rolled this out in production and seen that it works: no
increase in error rate, and temporary files do not hang around any more.

config/initializers/puma_client_tempfile_patch.rb

@@ -3,7 +3,6 @@
 if Gitlab::Runtime.puma?
   raise "Remove this monkey patch: #{__FILE__}" unless Puma::Const::VERSION == '5.1.1'
 
-  if ENV['GITLAB_TEMPFILE_IMMEDIATE_UNLINK'] == '1'
   # This is copied from https://github.com/puma/puma/blob/v5.1.1/lib/puma/client.rb,
   # with two additions: both times we create a temporary file, we immediately
   # call `#unlink`. This means that if the process gets terminated without being
@@ -99,5 +98,4 @@ if Gitlab::Runtime.puma?
       end
     end
   end
-  end
 end

lib/gitlab/middleware/rack_multipart_tempfile_factory.rb

@@ -14,9 +14,7 @@ module Gitlab
       end
 
       def call(env)
-        if ENV['GITLAB_TEMPFILE_IMMEDIATE_UNLINK'] == '1'
         env[Rack::RACK_MULTIPART_TEMPFILE_FACTORY] = FACTORY
-        end
 
         @app.call(env)
       end

spec/lib/gitlab/middleware/rack_multipart_tempfile_factory_spec.rb

@@ -42,11 +42,6 @@ RSpec.describe Gitlab::Middleware::RackMultipartTempfileFactory do
   context 'for a multipart request' do
     let(:env) { Rack::MockRequest.env_for('/', multipart_fixture) }
 
-    context 'when the environment variable is enabled' do
-      before do
-        stub_env('GITLAB_TEMPFILE_IMMEDIATE_UNLINK', '1')
-      end
-
     it 'immediately unlinks the temporary file' do
       tempfile = Tempfile.new('foo')
 
@@ -64,25 +59,6 @@ RSpec.describe Gitlab::Middleware::RackMultipartTempfileFactory do
     end
   end
 
-    context 'when the environment variable is disabled' do
-      it 'does not immediately unlink the temporary file' do
-        tempfile = Tempfile.new('foo')
-
-        expect(tempfile.path).not_to be(nil)
-        expect(Rack::Multipart::Parser::TEMPFILE_FACTORY).to receive(:call).and_return(tempfile)
-        expect(tempfile).not_to receive(:unlink).and_call_original
-
-        subject.call(env)
-
-        expect(tempfile.path).not_to be(nil)
-      end
-
-      it 'processes the request as normal' do
-        expect(subject.call(env)).to eq([200, { 'Content-Type' => 'image/jpeg' }, [file_contents]])
-      end
-    end
-  end
-
   context 'for a regular request' do
     let(:env) { Rack::MockRequest.env_for('/', params: { 'foo' => 'bar' }) }
 

spec/requests/api/projects_spec.rb

@@ -1634,7 +1634,6 @@ RSpec.describe API::Projects do
     end
 
     it "does not leave the temporary file in place after uploading, even when the tempfile reaper does not run" do
-      stub_env('GITLAB_TEMPFILE_IMMEDIATE_UNLINK', '1')
       tempfile = Tempfile.new('foo')
       path = tempfile.path