Replace wxEXPLICIT with the 'explicit' keyword

See #17655.

include/wx/qt/bitmap.h

@@ -32,7 +32,7 @@ public:
     
     // Convert from wxIcon / wxCursor
     wxBitmap(const wxIcon& icon) { CopyFromIcon(icon); }
-    wxEXPLICIT wxBitmap(const wxCursor& cursor);
+    explicit wxBitmap(const wxCursor& cursor);
 
     static void InitStandardHandlers();
 

include/wx/qt/glcanvas.h

@@ -31,7 +31,7 @@ private:
 class WXDLLIMPEXP_GL wxGLCanvas : public wxGLCanvasBase
 {
 public:
-    wxEXPLICIT // avoid implicitly converting a wxWindow* to wxGLCanvas
+    explicit // avoid implicitly converting a wxWindow* to wxGLCanvas
     wxGLCanvas(wxWindow *parent,
                wxWindowID id = wxID_ANY,
                const int *attribList = NULL,