HTTP Metrics: Incorrect API Request Example in Documentation for HTTP Metrics

### What happened? Hi, I came across an issue with the example provided for sending OTLP metrics using `requests` in Python. Specifically, the code has a few problems that make the request not work properly. Here's a summary of the issues: #### 1. **Incorrect `BODY` Definition**: In the code, the `BODY` variable is defined incorrectly. The string is wrapped with **single quotes** (`'`), but it contains an additional `data='...'`, which is not valid for constructing the body of the request. This should be a valid **JSON string**, not a wrapped string. #### 2. **Incorrect URL Format**: In the original code, you are constructing the URL like this: ```python URL = f"https://{HOST}/otlp/v1/metrics" ``` However, the `HOST` variable already includes the base URL, so adding `/otlp/v1/metrics` again creates a malformed URL. The correct URL is simply the `HOST` variable without the extra `/otlp/v1/metrics`. #### 3. **Incorrect `Content-Type` Header**: The `Content-Type` header is set to `text/plain`, but when sending JSON data in a POST request, it should be set to `application/json`. <img width="973" height="1374" alt="Image" src="https://github.com/user-attachments/assets/c39e05b3-2c2b-4b87-b5ea-11b404bf955d" /> In addition to curl, there are also issues with the code examples in other languages. ### What did you expect to happen? code without error ### Did this work before? don't know ### How do we reproduce it? 1. go to http metrics, such as https://liuweiqing.grafana.net/connections/add-new-connection/http-metrics ### Is the bug inside a dashboard panel? no ### Environment (with versions)? Grafana:Grafana Cloud (steady) OS: win11 Browser: chrome ### Grafana platform? I use Grafana Cloud ### Datasource(s)? HTTP Metrics