[WebDriver BiDi] Fix test for window.prompt opened (#46441)

* [WebDriver BiDi] Fix test for window.prompt opened

* fix other test as well

* Update webdriver/tests/bidi/browsing_context/user_prompt_opened/user_prompt_opened.py

Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>

---------

Co-authored-by: Maksim Sadym <69349599+sadym-chromium@users.noreply.github.com>

webdriver/tests/bidi/browsing_context/user_prompt_opened/user_prompt_opened.py

@@ -53,11 +53,14 @@ async def test_prompt_type(
         "context": new_tab["context"],
         "type": prompt_type,
         "message": text,
+        **({
+            "defaultValue": ""
+        } if prompt_type == 'prompt' else {})
     }
 
 
 @pytest.mark.parametrize(
-    "default", [None, "", "default"], ids=["null", "empty string", "non empty string"]
+    "default", [None, "", "default"], ids=["undefined", "empty string", "non empty string"]
 )
 async def test_prompt_default_value(
     bidi_session, inline, new_tab, subscribe_events, wait_for_event, wait_for_future_safe, default
@@ -68,7 +71,7 @@ async def test_prompt_default_value(
     text = "test"
 
     if default is None:
-        script = f"<script>window.prompt('{text}', null)</script>"
+        script = f"<script>window.prompt('{text}')</script>"
     else:
         script = f"<script>window.prompt('{text}', '{default}')</script>"
 
@@ -85,7 +88,9 @@ async def test_prompt_default_value(
         "message": text,
     }
 
-    if default is not None:
+    if default is None:
+        expected_event["defaultValue"] = ""
+    else:
         expected_event["defaultValue"] = default
 
     assert event == expected_event