dt-bindings: iio: dac: adi,ad5755: drop unrelated included.

Probably a cut and paste error, but the binding header used in the
example is for the wrong device and nothing from it is used.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Sean Nyekjaer <sean.nyekjaer@prevas.dk>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/iio/dac/adi,ad5755.yaml

@@ -125,7 +125,6 @@ oneOf:
 
 examples:
   - |
-    #include <dt-bindings/iio/adi,ad5592r.h>
     spi {
         #address-cells = <1>;
         #size-cells = <0>;