Fix syntax error in interface headers

Although these headers are not supposed to be compiled, it's still
better to avoid at least the obvious typos in them.

Closes https://github.com/wxWidgets/wxWidgets/pull/2140

interface/wx/propgrid/editors.h

@@ -251,7 +251,7 @@ public:
 class wxPGChoiceEditor : public wxPGEditor
 {
 public:
-    wxPGChoiceEditor()
+    wxPGChoiceEditor();
     virtual ~wxPGChoiceEditor();
 
     virtual wxPGWindowList CreateControls(wxPropertyGrid* propgrid,

interface/wx/propgrid/propgrid.h

@@ -1403,7 +1403,7 @@ public:
                  accessible even after the associated property or
                  the property grid has been deleted.
     */
-    wxVariant GetPropertyValue() const
+    wxVariant GetPropertyValue() const;
 
     /**
         Returns value of the associated property.

interface/wx/propgrid/propgridpagestate.h

@@ -376,7 +376,7 @@ public:
     */
     inline unsigned int GetActualVirtualHeight() const;
 
-    unsigned int GetColumnCount() const'
+    unsigned int GetColumnCount() const;
 
     int GetColumnMinWidth( int column ) const;
 
@@ -524,4 +524,4 @@ public:
     bool DoExpand( wxPGProperty* p );
 
     void CalculateFontAndBitmapStuff( int vspacing );
-}:
+};