Compile fix - use Utils::optional

Amends f83eeb0548

Change-Id: Iad1ca06bf546405873aaf8daebbdb76b79f4c0ff
Reviewed-by: hjk <hjk@qt.io>

src/plugins/fakevim/fakevimhandler.cpp

@@ -2419,7 +2419,7 @@ public:
 
         // If empty, cx{motion} will store the range defined by {motion} here.
         // If non-empty, cx{motion} replaces the {motion} with selectText(*exchangeData)
-        std::optional<Range> exchangeRange;
+        Utils::optional<Range> exchangeRange;
     } g;
 };