Increase lower DAG `needs` limit from five to ten

If the feature flag `ci_dag_limit_needs` is turned on for a GitLab
instance, a job can now depend on up to ten jobs instead of five

changelogs/unreleased/leipert-increase-dag-limit.yml

+---
+title: Increase lower DAG `needs` limit from five to ten
+merge_request: 21237
+author:
+type: changed

doc/ci/yaml/README.md

@@ -2256,11 +2256,11 @@ This example creates three paths of execution:
   pipeline will be created with YAML error.
 - We are temporarily limiting the maximum number of jobs that a single job can
   need in the `needs:` array:
-  - For GitLab.com, the limit is five. For more information, see our
+  - For GitLab.com, the limit is ten. For more information, see our
     [infrastructure issue](https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/7541).
   - For self-managed instances, the limit is:
-    - Five by default (`ci_dag_limit_needs` feature flag is enabled).
-    - 50 if the `ci_dag_limit_needs` feature flag is disabled.
+    - 10, if the `ci_dag_limit_needs` feature flag is enabled (default).
+    - 50, if the `ci_dag_limit_needs` feature flag is disabled.
 - It is impossible for now to have `needs: []` (empty needs), the job always needs to
   depend on something, unless this is the job in the first stage. However, support for
   an empty needs array [is planned](https://gitlab.com/gitlab-org/gitlab/issues/30631).

lib/gitlab/ci/pipeline/seed/build.rb

@@ -10,7 +10,7 @@ module Gitlab
           delegate :dig, to: :@seed_attributes
           # When the `ci_dag_limit_needs` is enabled it uses the lower limit
-          LOW_NEEDS_LIMIT = 5
+          LOW_NEEDS_LIMIT = 10
           HARD_NEEDS_LIMIT = 50
           def initialize(pipeline, attributes, previous_stages)

spec/lib/gitlab/ci/pipeline/seed/build_spec.rb

@@ -852,7 +852,7 @@ describe Gitlab::Ci::Pipeline::Seed::Build do
       it "returns an error" do
         expect(subject.errors).to contain_exactly(
-          "rspec: one job can only need 5 others, but you have listed 6. See needs keyword documentation for more details")
+          "rspec: one job can only need 10 others, but you have listed 11. See needs keyword documentation for more details")
       end
     end