Report Europe: fix figure reference.

src/Covid19MortalityEurope.Rmd

@@ -399,7 +399,7 @@ mortality peak:
   Montenegro, Albania, Czech Republic, and Croatia.
 
 Daily mortality rate has now reached a low level in most countries
-(fig. \@ref(fig:decay)). However, it is sill at least 50% of the
+(fig. \@ref(fig:fdecay)). However, it is sill at least 50% of the
 national peak mortality rate in `r collapse(persist, NA)`.
   
 These observations suggest that while the overall situation has much