Remove Gemini 3 Pro before deprecation date

Author: AnsonLai

src/taskpane/taskpane.html

@@ -98,7 +98,6 @@ <h3>Settings</h3>
       <option value="gemini-2.5-flash" selected>Gemini 2.5 Flash (Default)</option>
       <option value="gemini-3-flash-preview">Gemini 3 Flash Preview</option>
       <option value="gemini-2.5-pro">Gemini 2.5 Pro</option>
-      <option value="gemini-3-pro-preview">Gemini 3 Pro Preview</option>
       <option value="gemini-3.1-pro-preview">Gemini 3.1 Pro Preview</option>
     </select>
     <br />
@@ -108,7 +107,6 @@ <h3>Settings</h3>
       <option value="gemini-2.5-flash">Gemini 2.5 Flash</option>
       <option value="gemini-3-flash-preview">Gemini 3 Flash Preview</option>
       <option value="gemini-2.5-pro" selected>Gemini 2.5 Pro (Default)</option>
-      <option value="gemini-3-pro-preview">Gemini 3 Pro Preview</option>
       <option value="gemini-3.1-pro-preview">Gemini 3.1 Pro Preview</option>
     </select>
     <br />