Replace iron-autogrow-textarea with standard textarea

The `iron-autogrow-textarea` component has been removed in Change 495381
from the main Gerrit platform. This change updates the code owner check
tool to use the standard HTML `<textarea>` element instead.

Google-Bug-Id: b/437250084
Change-Id: I7bcf5f26ff49c2371c2926471969f9077e2e19e3

web/gr-check-code-owner.ts

diff --git a/web/gr-check-code-owner.ts b/web/gr-check-code-owner.ts
index 9215ba9..04f8ee5 100644
--- a/web/gr-check-code-owner.ts
+++ b/web/gr-check-code-owner.ts
@@ -50,7 +50,7 @@
   userInput!: HTMLInputElement;
 
   @query('#resultOutput')
-  resultOutput!: HTMLInputElement;
+  resultOutput!: HTMLTextAreaElement;
 
   @query('#noteAboutLimitedDebugInformation')
   noteAboutLimitedDebugInformation!: HTMLInputElement;
@@ -210,12 +210,12 @@
         </p>
         <section>
           <span class="value">
-            <iron-autogrow-textarea
+            <textarea
               class="output"
               id="resultOutput"
               readonly
             >
-            </iron-autogrow-textarea>
+            </textarea>
           </span>
         </section>
         <p