[DESKADP][DESKMON] Notify property sheet that DWLP_MSGRESULT is set

When FALSE is returned, Apply button ignores validation result
and becomes disabled after clicking as if settings were applied.
Fix it by setting the return value to TRUE.

See https://docs.microsoft.com/en-us/windows/win32/controls/psn-apply

dll/shellext/deskadp/deskadp.c

@@ -422,6 +422,7 @@ DisplayAdapterDlgProc(HWND hwndDlg,
                     SetWindowLongPtr(hwndDlg,
                                      DWLP_MSGRESULT,
                                      ApplyDisplayAdapterChanges(This));
+                    Ret = TRUE;
                     break;
                 }
 

dll/shellext/deskmon/deskmon.c

@@ -666,6 +666,7 @@ MonitorDlgProc(HWND hwndDlg,
                     SetWindowLongPtr(hwndDlg,
                                      DWLP_MSGRESULT,
                                      ApplyMonitorChanges(This));
+                    Ret = TRUE;
                     break;
                 }