Remove unused function Graphics::textboxcenter()

This function was marked as unused by cppcheck.

desktop_version/src/Graphics.cpp

@@ -2814,18 +2814,6 @@ void Graphics::setwarprect( int a, int b, int c, int d )
 	warprect.h = d;
 }
 
-void Graphics::textboxcenter()
-{
-	if (!INBOUNDS_VEC(m, textbox))
-	{
-		puts("textboxcenter() out-of-bounds!");
-		return;
-	}
-
-	textbox[m].centerx();
-	textbox[m].centery();
-}
-
 void Graphics::textboxcenterx()
 {
 	if (!INBOUNDS_VEC(m, textbox))

desktop_version/src/Graphics.h

@@ -49,8 +49,6 @@ public:
 
 	void createtextbox(std::string t, int xp, int yp, int r= 255, int g= 255, int b = 255);
 
-	void textboxcenter();
-
 	void textboxcenterx();
 
 	int textboxwidth();