docs: Update dependencies installation cell in steam toolkit (#15148)

**Description:** `decouple` is not the correct package, it's
`python-decouple`, and the notebook cell doesn't compile.

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docs/docs/integrations/toolkits/steam.ipynb

@@ -25,7 +25,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "!pip install python-steam-api, decouple"
+    "!pip install python-steam-api python-decouple"
    ]
   },
   {