Fix output

Co-authored-by: NachiaVivias <71425187+NachiaVivias@users.noreply.github.com>

graph/minimum_spanning_tree/task.md

@@ -46,7 +46,7 @@ $a_{M - 1}$ $b_{M - 1}$ $c_{M - 1}$
 
 ~~~
 $X$
-$e_0$ $e_1$ $e_2$ ... $e_{N - 1}$
+$e_0$ $e_1$ $e_2$ ... $e_{N - 2}$
 ~~~
 
 @{lang.en}