Utils: Fix compile with gcc4.9

Otherwise compile fails with
 constexpr constructor does not have empty body.
Broke with 4b0bcbdcb6.

Change-Id: I5f058cd4ef11dddb72c8fc88b7184d41f4ffc15a
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/libs/utils/sizedarray.h

@@ -55,7 +55,7 @@ public:
     using std::array<T, MaxSize>::crend;
 
     constexpr SizedArray() = default;
-    constexpr SizedArray(std::initializer_list<T> list)
+    SizedArray(std::initializer_list<T> list)
         : m_size(list.size())
     {
         std::copy(list.begin(), list.end(), begin());