Fix wxUIActionSimulator::Text() parameter documentation

This function explicitly accepts ASCII strings only, so it's limited to
"const char*", but was incorrectly documented as taking wxString.

Closes https://github.com/wxWidgets/wxWidgets/pull/1879

interface/wx/uiaction.h

@@ -176,8 +176,8 @@ public:
         keyboard layout but may not work with other layouts.
 
         @param text
-            The string to type.
+            The string, containing only US ASCII characters, to type.
     */
-    bool Text(const wxString& text);
+    bool Text(const char* text);
 };