libcamera: controls: Add missing period at end of Gamma description

The last sentence of the Gamma control description misses the final
period. Add it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/control_ids_core.yaml

@@ -870,6 +870,6 @@ controls:
       description:  |
         Specify a fixed gamma value. Default must be 2.2 which closely mimics 
         sRGB gamma. Note that this is camera gamma, so it is applied as 
-        1.0/gamma
+        1.0/gamma.
 
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