Remove test against DSA ssh keys because

we're not really supporting them out of the box. See:
https://gitlab.com/gitlab-org/gitlab-ce/issues/44363

qa/qa.rb

@@ -17,7 +17,6 @@ module QA
     module Key
       autoload :Base, 'qa/runtime/key/base'
       autoload :RSA, 'qa/runtime/key/rsa'
-      autoload :DSA, 'qa/runtime/key/dsa'
       autoload :ECDSA, 'qa/runtime/key/ecdsa'
       autoload :ED25519, 'qa/runtime/key/ed25519'
     end

qa/qa/runtime/key/dsa.rb

@@ -1,11 +0,0 @@
-module QA
-  module Runtime
-    module Key
-      class DSA < Base
-        def initialize
-          super('dsa', 1024)
-        end
-      end
-    end
-  end
-end

qa/qa/specs/features/project/deploy_key_clone_spec.rb

@@ -18,7 +18,6 @@ module QA
       Runtime::Key::RSA.new(2048),
       Runtime::Key::RSA.new(4096),
       Runtime::Key::RSA.new(8192),
-      Runtime::Key::DSA.new,
       Runtime::Key::ECDSA.new(256),
       Runtime::Key::ECDSA.new(384),
       Runtime::Key::ECDSA.new(521),

qa/spec/runtime/key/dsa_spec.rb

@@ -1,9 +0,0 @@
-describe QA::Runtime::Key::DSA do
-  describe '#public_key' do
-    subject { described_class.new.public_key }
-
-    it 'generates a public DSA key' do
-      expect(subject).to match(%r{\Assh\-dss AAAA[0-9A-Za-z+/]+={0,3}})
-    end
-  end
-end