Python: Fix Bing Connector Setting Usage (#6493)

### Motivation and Context

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[PR 6278](#6278) added
support for Bing Custom Search, but had a bug introduced when merging a
change to how settings worked.

### Description

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These notes will help understanding how your code works. Thanks! -->

This PR fixes the bug in how settings are referenced.

### Contribution Checklist

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- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Co-authored-by: Evan Mattson <[email protected]>

python/semantic_kernel/connectors/search_engine/bing_connector.py

@@ -62,11 +62,16 @@ async def search(self, query: str, num_results: int = 1, offset: int = 0) -> lis
 
         _base_url = (
             "https://api.bing.microsoft.com/v7.0/custom/search"
-            if self._custom_config
+            if self._settings.custom_config
             else "https://api.bing.microsoft.com/v7.0/search"
         )
-        _request_url = f"{_base_url}?q={urllib.parse.quote_plus(query)}&count={num_results}&offset={offset}" + (
-            f"&customConfig={self._custom_config}" if self._custom_config else ""
+        _request_url = (
+            f"{_base_url}?q={urllib.parse.quote_plus(query)}&count={num_results}&offset={offset}"
+            + (
+                f"&customConfig={self._settings.custom_config}"
+                if self._settings.custom_config
+                else ""
+            )
         )
 
         logger.info(f"Sending GET request to {_request_url}")