Fix typo: change 'insures' to 'ensures' in WPF Input Overview (#2137)

* Initial plan

* Fix typo: change 'insures' to 'ensures' in input-overview.md

Co-authored-by: adegeo <67293991+adegeo@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: adegeo <67293991+adegeo@users.noreply.github.com>

Author: Copilot

dotnet-desktop-guide/wpf/advanced/input-overview.md

@@ -356,7 +356,7 @@ For more information about keyboard focus, see [Focus Overview](focus-overview.m
 
 Logical focus refers to the <xref:System.Windows.Input.FocusManager.FocusedElement%2A?displayProperty=nameWithType> in a focus scope.  There can be multiple elements that have logical focus in an application, but there may only be one element that has logical focus in a particular focus scope.
 
-A focus scope is a container element that keeps track of the <xref:System.Windows.Input.FocusManager.FocusedElement%2A> within its scope.  When focus leaves a focus scope, the focused element will lose keyboard focus but will retain logical focus.  When focus returns to the focus scope, the focused element will obtain keyboard focus.  This allows for keyboard focus to be changed between multiple focus scopes but insures that the focused element within the focus scope remains the focused element when focus returns.
+A focus scope is a container element that keeps track of the <xref:System.Windows.Input.FocusManager.FocusedElement%2A> within its scope.  When focus leaves a focus scope, the focused element will lose keyboard focus but will retain logical focus.  When focus returns to the focus scope, the focused element will obtain keyboard focus.  This allows for keyboard focus to be changed between multiple focus scopes but ensures that the focused element within the focus scope remains the focused element when focus returns.
 
 An element can be turned into a focus scope in Extensible Application Markup Language (XAML) by setting the <xref:System.Windows.Input.FocusManager> attached property <xref:System.Windows.Input.FocusManager.IsFocusScope%2A> to `true`, or in code by setting the attached property by using the <xref:System.Windows.Input.FocusManager.SetIsFocusScope%2A> method.