[WIN32SS][NTUSER] Addendum to 0.4.12-dev-956-g0197c4f CORE-15893

Aims PixelPerfection for a regression that was introduced by
0.4.12-dev-954-g
1f619b2

and then improved already by
0.4.12-dev-956-g
0197c4f

The tweaking got ack of Jim Tabor. Test results:
https://reactos.org/testman/compare.php?ids=68026,68029

cherry-picked from 0.4.13-dev-397-g
3cc50ce

Author: JoachimHenze

win32ss/user/ntuser/winpos.c

@@ -960,7 +960,7 @@ co_WinPosGetMinMaxInfo(PWND Window, POINT* MaxSize, POINT* MaxPos,
 
     // Handle special case while maximized. CORE-15893
     if ((adjustedStyle & WS_THICKFRAME) && !(adjustedStyle & WS_CHILD) && !(adjustedStyle & WS_MINIMIZE))
-         adjust += 2;
+         adjust += 1;
 
     xinc = yinc = adjust;