removed unused file

doc/sphinx/include/vcl-backends.rst

-Backend declarations
---------------------
-
-A backend declaration creates and initializes a named backend object:
-::
-
-  backend www {
-    .host = "www.example.com";
-    .port = "http";
-  }
-
-The backend object can later be used to select a backend at request time:
-::
-
-  if (req.http.host ~ "(?i)^(www.)?example.com$") {
-    set req.backend = www;
-  }
-
-To avoid overloading backend servers, .max_connections can be set to
-limit the maximum number of concurrent backend connections.
-
-The timeout parameters can be overridden in the backend declaration.
-The timeout parameters are .connect_timeout for the time to wait for a
-backend connection, .first_byte_timeout for the time to wait for the
-first byte from the backend and .between_bytes_timeout for time to
-wait between each received byte.
-
-These can be set in the declaration like this:
-::
-
-  backend www {
-    .host = "www.example.com";
-    .port = "http";
-    .connect_timeout = 1s;
-    .first_byte_timeout = 5s;
-    .between_bytes_timeout = 2s;
-  }
-
-To mark a backend as unhealthy after number of items have been added
-to its saintmode list ``.saintmode_threshold`` can be set to the maximum
-list size. Setting a value of 0 disables saint mode checking entirely
-for that backend.  The value in the backend declaration overrides the
-parameter.
-