Added model specs

spec/models/protected_branch/merge_access_level_spec.rb

+require 'spec_helper'
+
+describe ProtectedBranch::MergeAccessLevel, :models do
+  it { is_expected.to validate_inclusion_of(:access_level).in_array([Gitlab::Access::MASTER, Gitlab::Access::DEVELOPER, Gitlab::Access::NO_ACCESS]) }
+end

spec/models/protected_branch/push_access_level_spec.rb

+require 'spec_helper'
+
+describe ProtectedBranch::PushAccessLevel, :models do
+  it { is_expected.to validate_inclusion_of(:access_level).in_array([Gitlab::Access::MASTER, Gitlab::Access::DEVELOPER, Gitlab::Access::NO_ACCESS]) }
+end