Clean up E0582 explanation

GuillaumeGomez · GuillaumeGomez · commit bb2ff593a63d · 2020-05-13T13:40:55.000+02:00
diff --git a/src/librustc_error_codes/error_codes/E0582.md b/src/librustc_error_codes/error_codes/E0582.md
@@ -1,5 +1,5 @@
-A lifetime appears only in an associated-type binding,
-and not in the input types to the trait.
+A lifetime is only present in an associated-type binding, and not in the input
+types to the trait.
 
 Erroneous code example:
 
