Fix wxTextCtrl border switching from dark mode

Do not check dark mode in wxTextCtrl::CanApplyThemeBorder(). Instead,
improve the checking for themed border drawing in the WM_NCPAINT
handler.

This fixed the border appearance after switching from dark mode to the
light one.

Closes #26794.

src/msw/textctrl.cpp

@@ -496,8 +496,8 @@ bool wxTextCtrl::Create(wxWindow *parent,
 // returns true if the platform should explicitly apply a theme border
 bool wxTextCtrl::CanApplyThemeBorder() const
 {
-    // Standard text control already handles theming in light mode.
-    return IsRich() || wxMSWDarkMode::IsActive();
+    // Standard text control already handles theming.
+    return IsRich();
 }
 
 bool wxTextCtrl::MSWCreateText(const wxString& value,

src/msw/window.cpp

@@ -3836,7 +3836,8 @@ wxWindowMSW::MSWHandleMessage(WXLRESULT *result,
             {
                 // Determine whether we should draw a border.
                 bool drawBorder = false;
-                wxBorder border = DoTranslateBorder(GetBorder());
+                wxBorder rawBorder = GetBorder();
+                wxBorder border = DoTranslateBorder(rawBorder);
                 switch ( border )
                 {
                     case wxBORDER_THEME:
@@ -3882,7 +3883,7 @@ wxWindowMSW::MSWHandleMessage(WXLRESULT *result,
                                       rcClient.right, rcClient.bottom);
 
                     // Draw the border.
-                    if ( border == wxBORDER_THEME )
+                    if ( rawBorder == wxBORDER_THEME )
                         MSWDrawThemeBorder(hdc);
                     else
                     {