ofAppGLFWWindow: close as private

It was confusing for some people who were calling it instead
of setWindowShouldClose and it's not needed from anywhere except
from the class itself

Fixes #6028

libs/openFrameworks/app/ofAppGLFWWindow.h

@@ -85,8 +85,6 @@ class ofAppGLFWWindow : public ofAppBaseGLWindow {
 	bool getWindowShouldClose();
 	void setWindowShouldClose();
 
-	void close();
-
 	void hideCursor();
 	void showCursor();
 
@@ -188,6 +186,8 @@ class ofAppGLFWWindow : public ofAppBaseGLWindow {
 	static void 	drop_cb(GLFWwindow* windowP_, int numFiles, const char** dropString);
 	static void		error_cb(int errorCode, const char* errorDescription);
 
+	void close();
+
 #ifdef TARGET_LINUX
 	void setWindowIcon(const std::string & path);
 	void setWindowIcon(const ofPixels & iconPixels);