docs(speedtest): update incorrect documentation

Each provider that implement the Provider interface expect to receive a
driver which should implement DriverInterface.

Doc was not updated.

Signed-off-by: Lionel Hubaut <lionel.hubaut@tessares.net>

src/speed_sleuth/provider/speedtest.py

@@ -38,17 +38,17 @@ class Speedtest(Provider):
     results as screenshots.
 
     Attributes:
-        browser: A browser instance that adheres to the BrowserInterface, used
-            for web interactions.
+        driver: A driver instance that adheres to the DriverInterface, used
+            for web interactions with the browser.
 
     """
 
     def __init__(self, driver: DriverInterface):
         """Initializes the Speedtest provider with a browser instance.
 
         Parameters:
-            browser: The browser instance through which the speed test will be
-                conducted on speedtest.net.
+            driver: A driver instance that adheres to the DriverInterface, used
+                for web interactions with the browser.
 
         """
         super().__init__(driver)