Remove Signature.vectorizes_over_list entirely (#9777)

# Description
With the current typechecking logic this property has no effect.
It was only used in the example testing, and provided some indication of
this vectorizing property.
With #9742 all commands that previously declared it have explicit list
signatures. If we want to get it back in the future we can reconstruct
it from the signature.

Simplifies the example testing a bit.

# User-Facing Changes
Causes a breaking change for plugins that previously declared it. While
this causes a compile fail, this was already broken by our more
stringent type checking.
This will be a good reminder for plugin authors to update their
signature as well to reflect the more stringent type checking.

crates/nu-command/src/math/abs.rs

@@ -19,7 +19,6 @@ impl Command for SubCommand {
                     Type::List(Box::new(Type::Number)),
                 ),
             ])
-            .vectorizes_over_list(true)
             .allow_variants_without_examples(true)
             .category(Category::Math)
     }

crates/nu-command/src/math/ceil.rs

@@ -19,7 +19,6 @@ impl Command for SubCommand {
                     Type::List(Box::new(Type::Number)),
                 ),
             ])
-            .vectorizes_over_list(true)
             .allow_variants_without_examples(true)
             .category(Category::Math)
     }

crates/nu-command/src/math/floor.rs

@@ -19,7 +19,6 @@ impl Command for SubCommand {
                     Type::List(Box::new(Type::Number)),
                 ),
             ])
-            .vectorizes_over_list(true)
             .allow_variants_without_examples(true)
             .category(Category::Math)
     }

crates/nu-command/src/math/log.rs

@@ -29,7 +29,6 @@ impl Command for SubCommand {
                 ),
             ])
             .allow_variants_without_examples(true)
-            .vectorizes_over_list(true)
             .category(Category::Math)
     }
 

crates/nu-command/src/math/round.rs

@@ -22,7 +22,6 @@ impl Command for SubCommand {
                     Type::List(Box::new(Type::Number)),
                 ),
             ])
-            .vectorizes_over_list(true)
             .allow_variants_without_examples(true)
             .named(
                 "precision",

crates/nu-command/src/math/sqrt.rs

@@ -19,7 +19,6 @@ impl Command for SubCommand {
                     Type::List(Box::new(Type::Number)),
                 ),
             ])
-            .vectorizes_over_list(true)
             .allow_variants_without_examples(true)
             .category(Category::Math)
     }