fix: allow_inf_nan option for Param subclasses

There was a typo in the __init__ method of the Param class which
misnamed the allow_inf_nan option in the kwargs passed to the
underlying Pydantic FieldInfo initializer.  This resulted in the
validator failing to enforce the constraint, and hence inf and nan
values being passed to the route handler where they should not have.

fastapi/params.py

@@ -91,7 +91,7 @@ class Param(FieldInfo):
             max_length=max_length,
             discriminator=discriminator,
             multiple_of=multiple_of,
-            allow_nan=allow_inf_nan,
+            allow_inf_nan=allow_inf_nan,
             max_digits=max_digits,
             decimal_places=decimal_places,
             **extra,

test_param_allow_inf_nan.py

@@ -0,0 +1,58 @@
+from typing import Optional
+
+from fastapi import FastAPI
+from fastapi.params import Query
+from fastapi.testclient import TestClient
+
+app = FastAPI()
+
+@app.get("/")
+def get(
+        x: Optional[float] = Query(default=0, allow_inf_nan=False),
+        y: Optional[float] = Query(default=0, allow_inf_nan=True),
+        z: Optional[float] = Query(default=0)) -> str:  # type: ignore
+    return 'OK'
+
+
+client = TestClient(app)
+
+
+def test_allow_inf_nan_false():
+    response = client.get('/?x=inf')
+    assert response.status_code == 422, response.text
+    
+    response = client.get('/?x=-inf')
+    assert response.status_code == 422, response.text
+    
+    response = client.get('/?x=nan')
+    assert response.status_code == 422, response.text
+
+    response = client.get('/?x=0')
+    assert response.status_code == 200, response.text
+
+def test_allow_inf_nan_true():
+    response = client.get('/?y=inf')
+    assert response.status_code == 200, response.text
+    
+    response = client.get('/?y=-inf')
+    assert response.status_code == 200, response.text
+    
+    response = client.get('/?y=nan')
+    assert response.status_code == 200, response.text
+
+    response = client.get('/?y=0')
+    assert response.status_code == 200, response.text
+
+def test_allow_inf_nan_not_specified():
+    response = client.get('/?z=inf')
+    assert response.status_code == 200, response.text
+    
+    response = client.get('/?z=-inf')
+    assert response.status_code == 200, response.text
+    
+    response = client.get('/?z=nan')
+    assert response.status_code == 200, response.text
+
+    response = client.get('/?z=0')
+    assert response.status_code == 200, response.text
+