community[patch]: raise_for_status logic missing in async _fetch of WebBaseLoader (#21948)

## 'raise_for_status' parameter of WebBaseLoader works in sync load but
not in async load.
In webBaseLoader:  

Sync load is calling `_scrape` and has `raise_for_status` properly
handled.
```
    def _scrape(
        self,
        url: str,
        parser: Union[str, None] = None,
        bs_kwargs: Optional[dict] = None,
    ) -> Any:
        from bs4 import BeautifulSoup

        if parser is None:
            if url.endswith(".xml"):
                parser = "xml"
            else:
                parser = self.default_parser

        self._check_parser(parser)

        html_doc = self.session.get(url, **self.requests_kwargs)
        if self.raise_for_status:
            html_doc.raise_for_status()

        if self.encoding is not None:
            html_doc.encoding = self.encoding
        elif self.autoset_encoding:
            html_doc.encoding = html_doc.apparent_encoding
        return BeautifulSoup(html_doc.text, parser, **(bs_kwargs or {}))
```
Async load is calling `_fetch` but missing `raise_for_status` logic.
```
    async def _fetch(
        self, url: str, retries: int = 3, cooldown: int = 2, backoff: float = 1.5
    ) -> str:
        async with aiohttp.ClientSession() as session:
            for i in range(retries):
                try:
                    async with session.get(
                        url,
                        headers=self.session.headers,
                        ssl=None if self.session.verify else False,
                        cookies=self.session.cookies.get_dict(),
                    ) as response:
                        return await response.text()
```

Co-authored-by: kefan.you <darkfss@sina.com>

libs/community/langchain_community/document_loaders/web_base.py

@@ -134,6 +134,8 @@ class WebBaseLoader(BaseLoader):
                         ssl=None if self.session.verify else False,
                         cookies=self.session.cookies.get_dict(),
                     ) as response:
+                        if self.raise_for_status:
+                            response.raise_for_status()
                         return await response.text()
                 except aiohttp.ClientConnectionError as e:
                     if i == retries - 1: