Revert CODEOWNERS validation of Web requests in diff check

This reverts commit 4d73ef61.

This was causing merges to fail when groups were used in CODEOWNERS:
https://gitlab.com/gitlab-org/gitlab/-/issues/216345.

changelogs/unreleased/sh-revert-codeowners-check.yml

+---
+title: Revert CODEOWNERS validation of Web requests in diff check
+merge_request: 30936
+author:
+type: fixed

ee/lib/ee/gitlab/checks/diff_check.rb

@@ -12,7 +12,7 @@ module EE
         def path_validations
           validations = [super].flatten
 
-          if project.branch_requires_code_owner_approval?(branch_name)
+          if !updated_from_web? && project.branch_requires_code_owner_approval?(branch_name)
             validations << validate_code_owners
           end
 
@@ -34,13 +34,11 @@ module EE
           matched_rules = loader.entries.collect { |e| "- #{e.pattern}" }
           code_owner_path = project.repository.code_owners_blob(ref: branch_name).path || "CODEOWNERS"
 
-          msg = "Pushes to protected branches that contain changes to files that\n" \
+          "Pushes to protected branches that contain changes to files that\n" \
             "match patterns defined in `#{code_owner_path}` are disabled for\n" \
             "this project. Please submit these changes via a merge request.\n\n" \
             "The following pattern(s) from `#{code_owner_path}` were matched:\n" \
             "#{matched_rules.join('\n')}\n"
-
-          updated_from_web? ? msg.tr("\n", " ") : msg
         end
 
         def validate_path_locks?

ee/spec/lib/gitlab/checks/diff_check_spec.rb

@@ -89,22 +89,8 @@ describe Gitlab::Checks::DiffCheck do
             stub_feature_flags(sectional_codeowners: false)
           end
 
-          context "for a non-web-based request" do
-            it "returns an error message" do
-              expect(validation_result).to include("Pushes to protected branches")
-              expect(validation_result).to include("\n")
-            end
-          end
-
-          context "for a web-based request" do
-            before do
-              expect(subject).to receive(:updated_from_web?).and_return(true)
-            end
-
-            it "returns an error message with newline chars removed" do
-              expect(validation_result).to include("Pushes to protected branches")
-              expect(validation_result).not_to include("\n")
-            end
+          it "returns an error message" do
+            expect(validation_result).to include("Pushes to protected branches")
           end
         end
 
@@ -142,16 +128,30 @@ describe Gitlab::Checks::DiffCheck do
       end
 
       context "when the feature is enabled on the project" do
-        before do
-          expect(project).to receive(:branch_requires_code_owner_approval?)
-            .once.and_return(true)
+        context "updated_from_web? == false" do
+          before do
+            expect(subject).to receive(:updated_from_web?).and_return(false)
+            expect(project).to receive(:branch_requires_code_owner_approval?)
+              .once.and_return(true)
+          end
+
+          it "returns an array of Proc(s)" do
+            validations = subject.send(:path_validations)
+
+            expect(validations.any?).to be_truthy
+            expect(validations.any? { |v| !v.is_a? Proc }).to be_falsy
+          end
         end
 
-        it "returns an array of Proc(s)" do
-          validations = subject.send(:path_validations)
+        context "updated_from_web? == true" do
+          before do
+            expect(subject).to receive(:updated_from_web?).and_return(true)
+            expect(project).not_to receive(:branch_requires_code_owner_approval?)
+          end
 
-          expect(validations.any?).to be_truthy
-          expect(validations.any? { |v| !v.is_a? Proc }).to be_falsy
+          it "returns an empty array" do
+            expect(subject.send(:path_validations)).to eq([])
+          end
         end
       end
     end