Plurals in format redundant arguments suggestion

Author: francorbacho

compiler/rustc_builtin_macros/messages.ftl

@@ -137,7 +137,10 @@ builtin_macros_format_positional_after_named = positional arguments cannot follo
     .label = positional arguments must be before named arguments
     .named_args = named argument
 
-builtin_macros_format_redundant_args = redundant argument
+builtin_macros_format_redundant_args = redundant {$n ->
+    [one] argument
+    *[more] arguments
+    }
     .help = {$n ->
         [one] the formatting string already captures the binding directly, it doesn't need to be included in the argument list
         *[more] the formatting strings already captures the bindings directly, they don't need to be included in the argument list

tests/ui/did_you_mean/issue-105225.stderr

@@ -34,7 +34,7 @@ note: the formatting specifier is referencing the binding already
 LL |     println!("{} {x}", x, x);
    |                   ^
 
-error: redundant argument
+error: redundant arguments
   --> $DIR/issue-105225.rs:13:14
    |
 LL |     println!("{x} {y}", x, y);
@@ -51,7 +51,7 @@ LL -     println!("{x} {y}", x, y);
 LL +     println!("{x} {y}", );
    |
 
-error: redundant argument
+error: redundant arguments
   --> $DIR/issue-105225.rs:17:14
    |
 LL |     println!("{} {} {x} {y} {}", x, x, x, y, y);