Remediate use of "blacklist" in push rule check error

Also:

- #inspect will produce nicer output
- 'prohibited' is sufficient
- revise tests to expect the updated push rule check error

ee/changelogs/unreleased/bprescott-20210408-denylist.yml

+---
+title: Change use of "blacklist" to "denylist" in push rule check error
+merge_request: 58868
+author:
+type: changed

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

@@ -72,7 +72,7 @@ module EE
             if changed_path.new_file? && denylisted_regex = push_rule.filename_denylisted?(changed_path.path)
               return unless denylisted_regex.present?
 
-              "File name #{changed_path.path} was blacklisted by the pattern #{denylisted_regex}."
+              "File name #{changed_path.path} was prohibited by the pattern #{denylisted_regex.inspect}."
             end
           rescue ::PushRule::MatchError => e
             raise ::Gitlab::GitAccess::ForbiddenError, e.message

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

@@ -191,7 +191,7 @@ RSpec.describe Gitlab::Checks::DiffCheck do
         it_behaves_like 'check ignored when push rule unlicensed'
 
         it "returns an error if a new or renamed filed doesn't match the file name regex" do
-          expect { subject.validate! }.to raise_error(Gitlab::GitAccess::ForbiddenError, "File name README was blacklisted by the pattern READ*.")
+          expect { subject.validate! }.to raise_error(Gitlab::GitAccess::ForbiddenError, "File name README was prohibited by the pattern \"READ*\".")
         end
 
         it 'returns an error if the regex is invalid' do
@@ -247,7 +247,7 @@ RSpec.describe Gitlab::Checks::DiffCheck do
               project.repository.commits_between(old_rev, new_rev)
             )
 
-            expect { subject.validate! }.to raise_error(Gitlab::GitAccess::ForbiddenError, /File name #{file_path} was blacklisted by the pattern/)
+            expect { subject.validate! }.to raise_error(Gitlab::GitAccess::ForbiddenError, /File name #{file_path} was prohibited by the pattern/)
           end
         end
       end

qa/qa/specs/features/ee/browser_ui/3_create/repository/push_rules_spec.rb

@@ -55,7 +55,7 @@ module QA
           expect_error_on_push(file: large_file,
             error: 'File "file" is larger than the allowed size of 1 MB')
           expect_error_on_push(file: wrongly_named_file,
-            error: Regexp.escape("File name #{@file_name_limitation} was blacklisted by the pattern #{@file_name_limitation}"))
+            error: Regexp.escape("File name #{@file_name_limitation} was prohibited by the pattern #{@file_name_limitation}"))
         end
 
         it 'restricts users by email format', testcase: 'https://gitlab.com/gitlab-org/quality/testcases/-/issues/652' do
@@ -86,7 +86,7 @@ module QA
           }]
 
           expect_error_on_push(file: secret_file,
-            error: Regexp.escape('File name id_rsa was blacklisted by the pattern id_rsa$'))
+            error: Regexp.escape('File name id_rsa was prohibited by the pattern id_rsa$'))
         end
 
         it 'restricts removal of tag', testcase: 'https://gitlab.com/gitlab-org/quality/testcases/-/issues/650' do