Fix wxDC::DrawRectangle() when using RTL in wxMSW.

Extend the correct edge of the rectangle (always the physical right, not the
logical right) to fix off by one errors in RTL mode, affecting notably wxGrid.

See #16250.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@77027 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Remove manual mirroring in RTL case from wxGrid code.

This is not necessary as wxDC already inherits RTL from the window itself and,
in fact, breaks the display when using RTL.

Closes #16250.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@77037 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775