urequests: Explicitly add "Connection: close" to request headers.

Even though we use HTTP 1.0, where closing connection after sending
response should be the default, some servers ignore this requirement and
keep the connection open.  So, explicitly send corresponding header to get
the expected behavior.

python-ecosys/urequests/urequests.py

@@ -81,7 +81,7 @@ def request(method, url, data=None, json=None, headers={}, stream=None, parse_he
             s.write(b"Content-Type: application/json\r\n")
         if data:
             s.write(b"Content-Length: %d\r\n" % len(data))
-        s.write(b"\r\n")
+        s.write(b"Connection: close\r\n\r\n")
         if data:
             s.write(data)