GL: mark the 4-argument DynamicAttribute constructor as explicit.

Should have been done since ever, considering it was not annotated with
/*implicit*/.

doc/changelog.dox

@@ -258,6 +258,9 @@ See also:
     @ref Animation library was changed to allow mutable access to the keys &
     values it references. Existing code needs to be changed to say
     @cpp TrackView<const K, const V> @ce instead of @cpp TrackView<K, V> @ce.
+-   The 4-argument @ref GL::DynamicAttribute constructor was not marked as
+    @cpp explicit @ce by mistake, it's done now to enforce readability in long
+    expressions.
 -   @ref Math::Matrix3::scaling() const and @ref Math::Matrix4::scaling() const
     now return a signed scaling vector instead of unsigned in order to prevent
     information loss. To restore the old behavior, apply @ref Math::abs() on

src/Magnum/GL/Attribute.h

@@ -513,13 +513,13 @@ class DynamicAttribute {
          * @param components    Component count
          * @param dataType      Type of passed data
          */
-        constexpr DynamicAttribute(Kind kind, UnsignedInt location, Components components, DataType dataType): _kind{kind}, _location{location}, _components{components}, _dataType{dataType} {}
+        constexpr explicit DynamicAttribute(Kind kind, UnsignedInt location, Components components, DataType dataType): _kind{kind}, _location{location}, _components{components}, _dataType{dataType} {}
 
         /**
          * @brief Construct from a compile-time attribute
          * @m_since{2019,10}
          */
-        template<UnsignedInt location_, class T> constexpr DynamicAttribute(const Attribute<location_, T>& attribute);
+        template<UnsignedInt location_, class T> constexpr /*implicit*/ DynamicAttribute(const Attribute<location_, T>& attribute);
 
         /** @brief Attribute kind */
         constexpr Kind kind() const { return _kind; }