Fixed generate command signature (#13200)

# Description

Removes `list<any>` as an input type for the `generate` command. This
command does not accept pipeline input (and cannot, logically). This can
be seen by the use of `_input` in the command's `run()`.

Also, due to #13199, in order to pass `toolkit check pr`, one of the
examples was changed to remove the `result`. This is probably a better
demonstration of the ability of the command to infinitely generate a
list anyway, and an infinite list can't be represented in a `result`.

# User-Facing Changes

Should only be a change to the help. The input type was never valid and
couldn't have been used.

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

crates/nu-command/src/generators/generate.rs

@@ -12,13 +12,7 @@ impl Command for Generate {
 
  fn signature(&self) -> Signature {
  Signature::build("generate")
- .input_output_types(vec![
- (Type::Nothing, Type::List(Box::new(Type::Any))),
- (
- Type::List(Box::new(Type::Any)),
- Type::List(Box::new(Type::Any)),
- ),
- ])
+ .input_output_types(vec![(Type::Nothing, Type::List(Box::new(Type::Any)))])
  .required("initial", SyntaxShape::Any, "Initial value.")
  .required(
  "closure",
@@ -63,23 +57,10 @@ used as the next argument to the closure, otherwise generation stops.
  )),
  },
  Example {
- example: "generate [0, 1] {|fib| {out: $fib.0, next: [$fib.1, ($fib.0 + $fib.1)]} } | first 10",
- description: "Generate a stream of fibonacci numbers",
- result: Some(Value::list(
- vec![
- Value::test_int(0),
- Value::test_int(1),
- Value::test_int(1),
- Value::test_int(2),
- Value::test_int(3),
- Value::test_int(5),
- Value::test_int(8),
- Value::test_int(13),
- Value::test_int(21),
- Value::test_int(34),
- ],
- Span::test_data(),
- )),
+ example:
+ "generate [0, 1] {|fib| {out: $fib.0, next: [$fib.1, ($fib.0 + $fib.1)]} }",
+ description: "Generate a continuous stream of Fibonacci numbers",
+ result: None,
  },
  ]
  }