[Community]: requests_kwargs not being used in _fetch (#28646)

- **Description:** `requests_kwargs` is not being passed to `_fetch`
which is fetching pages asynchronously. In this PR, making sure that we
are passing `requests_kwargs` to `_fetch` just like `_scrape`.
- **Issue:** #28634

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/document_loaders/web_base.py

@@ -208,7 +208,10 @@ class WebBaseLoader(BaseLoader):
                     )
                     if not self.session.verify:
                         kwargs["ssl"] = False
-                    async with session.get(url, **kwargs) as response:
+
+                    async with session.get(
+                        url, **(self.requests_kwargs | kwargs)
+                    ) as response:
                         if self.raise_for_status:
                             response.raise_for_status()
                         return await response.text()