Fix FINDA timer

We want to set the FINDA state IF the timer has not expired.
It is helpful to see why by looking at the commit which broke
this https://github.com/prusa3d/Prusa-Firmware/pull/3365/commits/802b8860c862f1e8cca82146ab70c0a0cadf2629

Without this fix my FINDA sensor just shows N/A. But after this commit is works perfectly.

Firmware/ultralcd.cpp

@@ -3497,7 +3497,7 @@ static void lcd_show_sensors_state()
 	uint8_t idler_state = STATE_NA;
 
 	pinda_state = READ(Z_MIN_PIN);
-	if (mmu_enabled && mmu_last_finda_response.expired(1000))
+	if (mmu_enabled && !mmu_last_finda_response.expired(1000))
 	{
 		finda_state = mmu_finda;
 	}