Stop event_commit_title from escaping its output

Return a non-html-safe, unescaped String instead of ActiveSupport::SafeBuffer
to preserve safety when the output is misused. Currently there's oly one user,
which does the right thing.

Closes #23311

app/helpers/events_helper.rb

@@ -154,7 +154,7 @@ module EventsHelper
   end
 
   def event_commit_title(message)
-    escape_once(truncate(message.split("\n").first, length: 70))
+    (message.split("\n").first || "").truncate(70)
   rescue
     "--broken encoding"
   end

spec/helpers/events_helper_spec.rb

@@ -62,4 +62,21 @@ describe EventsHelper do
       expect(helper.event_note(input)).to eq(expected)
     end
   end
+
+  describe '#event_commit_title' do
+    let(:message) { "foo & bar " + "A" * 70 + "\n" + "B" * 80 }
+    subject { helper.event_commit_title(message) }
+
+    it "returns the first line, truncated to 70 chars" do
+      is_expected.to eq(message[0..66] + "...")
+    end
+
+    it "is not html-safe" do
+      is_expected.not_to be_a(ActiveSupport::SafeBuffer)
+    end
+
+    it "handles empty strings" do
+      expect(helper.event_commit_title("")).to eq("")
+    end
+  end
 end