remove the deprecated index argument from filter commands' closure signature (#14594)

# Description

A lot of filter commands that have a closure argument (`each`, `filter`,
etc), have a wrong signature for the closure, indicating an extra int
argument for the closure.

I think they are a left over from before `enumerate` was added, used to
access iteration index. None of the commands changed in this PR actually
supply this int argument.

# User-Facing Changes
N/A

# Tests + Formatting
- 🟢 toolkit fmt
- 🟢 toolkit clippy
- 🟢 toolkit test
- 🟢 toolkit test stdlib

# After Submitting
N/A

crates/nu-cmd-extra/src/extra/filters/each_while.rs

@@ -25,7 +25,7 @@ impl Command for EachWhile {
             )])
             .required(
                 "closure",
-                SyntaxShape::Closure(Some(vec![SyntaxShape::Any, SyntaxShape::Int])),
+                SyntaxShape::Closure(Some(vec![SyntaxShape::Any])),
                 "the closure to run",
             )
             .category(Category::Filters)