Algorithm: Mark output of filtered as Q_REQUIRED_RESULT

Change-Id: I0518ed3c649efc8854cb5ef63c02e4def984cdd2
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/libs/utils/algorithm.h

@@ -341,6 +341,7 @@ auto transform(const SC &container, R (S::*p)() const)
 // filtered
 /////////////////
 template<typename C, typename F>
+Q_REQUIRED_RESULT
 C filtered(const C &container, F predicate)
 {
   C out;