update gitlab shell to remove git_protocol env var

lib/gitlab_shell.rb

@@ -180,7 +180,6 @@ class GitlabShell # rubocop:disable Metrics/ClassLength
       'GL_ID' => @gl_id,
       'GL_PROTOCOL' => GL_PROTOCOL,
       'GL_REPOSITORY' => @gl_repository,
-      'GIT_PROTOCOL' => @git_protocol,
       'GL_USERNAME' => @username
     }
     if @gitaly && @gitaly.include?('token')

spec/gitlab_shell_spec.rb

@@ -463,7 +463,6 @@ describe GitlabShell do
         'GL_PROTOCOL' => 'ssh',
         'GL_REPOSITORY' => gl_repository,
         'GL_USERNAME' => 'testuser',
-        'GIT_PROTOCOL' => 'version=2'
       }
     end
     let(:exec_options) { { unsetenv_others: true, chdir: ROOT_PATH } }