Update protected branch merge access for security policy project

This commit updates merge access from
developer to maintainer for security policy project's default
protected branch.
Changelog: fixed
EE: true

ee/app/services/security/security_orchestration_policies/project_create_service.rb

@@ -30,7 +30,7 @@ module Security
         params = {
           name: policy_project.default_branch_or_main,
           push_access_levels_attributes: [{ access_level: Gitlab::Access::NO_ACCESS }],
-          merge_access_levels_attributes: [{ access_level: Gitlab::Access::DEVELOPER }]
+          merge_access_levels_attributes: [{ access_level: Gitlab::Access::MAINTAINER }]
         }
 
         if protected_branch.present?

ee/spec/services/security/security_orchestration_policies/project_create_service_spec.rb

@@ -23,7 +23,7 @@ RSpec.describe Security::SecurityOrchestrationPolicies::ProjectCreateService do
         expect(project.security_orchestration_policy_configuration.security_policy_management_project).to eq(policy_project)
         expect(policy_project.namespace).to eq(project.namespace)
         expect(policy_project.protected_branches.map(&:name)).to contain_exactly(project.default_branch_or_main)
-        expect(policy_project.protected_branches.first.merge_access_levels.map(&:access_level)).to eq([Gitlab::Access::DEVELOPER])
+        expect(policy_project.protected_branches.first.merge_access_levels.map(&:access_level)).to eq([Gitlab::Access::MAINTAINER])
         expect(policy_project.protected_branches.first.push_access_levels.map(&:access_level)).to eq([Gitlab::Access::NO_ACCESS])
         expect(policy_project.team.developers).to contain_exactly(maintainer)
       end