Don't check for buffers or scale when Cursor::set_scale is called.

In the grand scheme of things, the cursor isn't scaled nor is it
shown/hidden that much. So this check doesn't help much, while breaking
tests

src/platforms/atomic-kms/server/kms/cursor.cpp

@@ -427,9 +427,6 @@ void mir::graphics::atomic::Cursor::set_scale(float new_scale)
 {
     std::lock_guard lg(guard);
 
-    if(!argb8888.empty() && new_scale == current_scale)
-        return;
-
     current_scale = new_scale;
     size = current_cursor_image->size() * new_scale;
     auto const scaled_cursor_buf = mg::scale_cursor_image(current_cursor_image, new_scale);

src/platforms/gbm-kms/server/kms/cursor.cpp

@@ -428,9 +428,6 @@ void mir::graphics::gbm::Cursor::set_scale(float new_scale)
 {
     std::lock_guard lg(guard);
 
-    if(!argb8888.empty() && new_scale == current_scale)
-        return;
-
     current_scale = new_scale;
     size = current_cursor_image->size() * new_scale;
     auto const scaled_cursor_buf = mg::scale_cursor_image(current_cursor_image, new_scale);

src/platforms/wayland/cursor.cpp

@@ -115,9 +115,6 @@ void mir::platform::wayland::Cursor::set_scale(float new_scale)
     {
         std::lock_guard lock{mutex};
 
-        if(buffer && new_scale == current_scale)
-            return;
-
         current_scale = new_scale;
 
         if (buffer) wl_buffer_destroy(buffer);

src/server/graphics/software_cursor.cpp

@@ -210,9 +210,6 @@ void mir::graphics::SoftwareCursor::set_scale(float new_scale)
 {
     std::lock_guard lg{guard};
 
-    if(renderable && new_scale == current_scale)
-        return;
-
     current_scale = new_scale;
     auto const to_remove = renderable? renderable: nullptr;
     renderable = create_scaled_renderable_for_current_cursor(new_scale);